Nephi was indeed a mighty prophet to have the Lord give him these powers! Because Nephi was diligent and sought the Lord’s will with “unwearyingness” the Lord gave Nephi power to seal things in heaven and on Earth. The key word in this chapter is unwearyingness. This is the type of attitude the Lord wishes that we all have when it comes to building His kingdom on the earth.
Repentance is a lot like exercise and keeping the body fit. If we exercise on a daily basis, then our bodies stay fit and toned. Once our bodies are in shape, keeping them fit requires little effort compared to getting them fit. But once we stop exercising regularly, our bodies fall out of shape. When we begin exercising again, the road to fitness is very difficult at first, but with persistence and discipline, we are fit again.
Therefore, we must repent on a daily basis. I recall reading something by Elder Eyring which talked about daily repentance. He knelt every night and asked Heavenly Father where he had gone amiss that day and then he repented of it. This greatly improved his spiritual sensitivity. In another talk (Henry B. Eyring, “Because of Your Steadiness,” Ensign, May 1988, 39), he mentions a quote, from President George Q. Cannon, that he keeps with him. President Cannon counseled, "Some people have an idea that because they have entered the waters of baptism and repented of their sins then that is an end of it. What a mistake! We need to have this spirit of repentance continually; we need to pray to God to show us our conduct every day. Every night before we retire to rest we should review the thoughts, words, and acts of the day and then repent of everything we have done that is wrong or that has grieved the Holy Spirit. Live this way every day and endeavor to progress every day. (Gospel Truth, Jerreld L. Newquist, ed., Salt Lake City: Deseret Book Co., 1987, p. 129)
If we try to do this every night when we pray, then we will become more keenly aware of the spirit and learn where we can improve in our life.