I lack strength in Christ, and have no confidence in what I do. What should I do? Does your Grace know of any books on boosting confidence in God and the self?
God is the source of all power with whom we can do everything "I can do all things through Christ who strengthens me" (Phil 4:13); and without Whom we can do nothing (John 15:5) and with Him we can do everything.
I suggest your read H.H. Pope Shenouda's book 'Ten Concepts'. It has a whole chapter on the concept of power and is available at: http://tasbeha.org/content/hh_books/Tenconcp/index.html.