The Torah tells us that when the Jewish people were preparing to leave Mitzrayim, Moshe Rabbeinu was being osek in the mitzvo of taking the remains of Yosef Hatzadik to be buried in Eretz Yisroel. The Gemara in Sotah quotes a passuk from Yehoshua which seems to contradict the Torah’s account here; the passuk there states that the Jewish people, not Moshe, brought the bones of Yosef to Eretz Yisroel. The Gemara answers with a principle that if a person begins a mitzvo and does not complete it but then someone else does so, then the Torah credits the completer (‘gomer’) with having fulfilled the mitzvo. Moshe only began the mitzvo of burying Yosef but did not complete it, therefore it is not credited to him, rather to the Bney Yisroel, who completed it.
There is another Medrash that seems to contradict this concept: The Medrash Shocher Tov says that David HaMelech is credited with building the Beis HaMikdash as it says in Tehillim, “Mizmoor shir Chanukas habayis leDavid,” even though David only began the building but did not complete it. This implies that the main credit is attributed to the ‘beginner’, (‘maschil’) not the ‘gomer’. Rav Moshe Feinstein zt”l resolves this contradiction: He writes that if the maschil did not complete the mitzvo through no fault of his own then he is credited with it even though he did not finish it. However, if he bears even the slightest guilt for not completing the mitzvo then it is credited to the gomer. David HaMelech bore absolutely no responsibility for his inability to complete the binyan Beis Hamikdash. Hashem told him that he could not do so, therefore, its binyan is attributed to him. In contrast, Moshe Rabbeinu could not complete the mitzvo of buying Yosef because he did not enter Eretz Yisroel. He did not enter Eretz Yisroel because of the chet at Mei Meriva, consequently his inability to complete the burial of Yosef was somewhat due to his actions. This explains why the burial of Yosef is not attributed to him.
Moshe Rabbeinu’s guilt in this instance is minimal, and yet it is sufficient to deny him the merit of the mitzvo of the burial of Yosef. The same is surely true of situations in our lives when we have the opportunity to complete some kind of mitzvo but we fail to do so because of our lack of persistence. This applies greatly to learning - when a new shiur begins there are often large numbers of people present but as the weeks go on, gradually less and less appear. Rav Yaakov Kamenetsky zt”l noted this phenomena with regard to daf yomi - he joked that many people being the new cycle with Berachos, but by the next Masechta, ‘ba Shabbos ba menucha’.
Another common area of failing in persistence is growth. For example, on certain occasions such as the Aseres Yemay Teshuva or times of suffering, people are inspired to make kabbalos to grow in a certain way. However, with the passage of time, these kabbalos often become distant memories. What aitsos are there that can make it more likely that we will be able to persist with our commitments?
The Chofetz Chaim zt”l wrote the Mishna Berurah over the course of twenty-five years - during this time he suffered many tribulations which hindered the writing of the sefer. The vast majority of people would have capitulated under such travails, seeing them as a simun that this undertaking was not meant to succeed. However, the Chofetz Chaim realized that all the challenges were all sent by the yetser hara to prevent the Mishna Berurah being written. Accordingly, he persisted and succeeded in writing one of the most important sefarim of the past hundred years. He was able to persist because he recognized the vital importance of what he was trying to do - this enabled him to overcome all the challenges and complete the Mishna Berurah. This provides us with one aitsa of how to succeed in our undertakings - if we can remain focused on the significance of what we are trying to do then we will have more chance of persisting.
One may argue that we do indeed have moments of inspiration where, like the Chofetz Chaim, we recognize the significance of our projects. However, with time it is difficult to maintain this level of inspiration and we are unable to persist. Rav Chaim Shmuelevitz zt”l addresses this problem. He discusses the case of Palti ben Layish. David married the daughter of Shaul HaMelech but Shaul believed that it was an invalid kiddushin and he gave Michal to be married to Palti. Palti suspected that David’s kiddushin was valid and therefore undertook not to touch Michal. Right at the beginning of their ’marriage’ he stuck a sword between them and said that anyone who acts improperly should be struck by this sword. Rav Shmuelevitz asks, what exactly did this act achieve? If his yetser would overcome him how would the sword stop him? He was the one who stuck the sword and he could remove it whenever he wanted.
Rav Shmuelevitz explains that at the beginning of this nisayon Palti attained a powerful recognition of how terrible it would be to do such an impropriety. However, he feared that over the course of time this clarity would weaken and he may fall to the temptations of the yetser hara. In order to prevent his from happening, at the very moment of inspiration he stuck the sword in between them and that sword would serve as a reminder of the power of his initial convictions.
In a similar vein, Rav Yisroel Reisman Shlita tells a story of a bachur in Volozhin Yeshiva who was known as being fluent in Shas. On one occasion he was eating a meal, and a friend came in asking for the location of a certain opinion. Whilst the bachur was struggling with this question someone else pointed out that Tosefos explicitly expressed this opinion. The bachur was so shaken by the fact that he missed an open Tosefos that he immediately left in the middle of the seudah and ran to the beis medrash. He continued learning with super-human hasmada, never leaving the beis medrash for the next 7 years and he became a Gadol. Someone present at the time noticed that the bachur left his meal so quickly that he did not bentsch! He asked Rav Chaim Volozhin zt”l if it was mutar to not bentsch in such a scenario. He answered that he could not say whether it was mutar or not, but that had the bachur bentsched and not left the seudah immediately then he would not have become a Gadol. At that moment he was struck by a deep sense of pain at his lack of knowledge and he utilized the power of this moment to begin learning on a new level. Had he waited even a few minutes he would have lost that inspiration forever.
So too in our lives we experience moments of inspiration where we attain a heightened sense of awareness of an important inyan. But the inspiration often wears away - we see from the above stories that one way of maintaining the inspiration is by doing a concrete act right away, and hopefully this act will help keep the momentum. An example of this is when we hear a powerful piece of mussar that we should act upon it by immediately beginning to put it into action. Another example is when we attain a heightened sense of closeness to G-d that we try to do something to help remember and tap into that moment. Rav Noach Orlowek Shlita suggests taking an internal ‘photograph’ of that moment so that you can always ‘look at it’ when you want inspiration and tap into that powerful moment. These are possible ways in which we can strive to not just begin endeavors but to complete them as well.
 Tehillim, 30:1.
 Medrash Shocher Tov, 122:1.
 Igros Moshe, Choshen Mishpat, 1st Chelek, Simun 49, Anaf 2, dh:uleanitus daati. See there for the answer of Shevus Yaakov and Rav Feinstein’s kashas on it. Also see Otsros Megadim, Beshalach, for a third approach.
 Sichos Mussar, Maamer 11, p.46.
 Sanhedrin 19b.