When you get down, or feel like hope is lost, or when you have done something you know is wrong, remember the following:

God knows, you are sorry, if that is what you truly feel in your heart.
The Apostle Paul in I Corinthians talks about how Satan buffeted him, and he was weak, and every once in a while, he had this one sin that he just had to do. When Paul finally asked God if he was going to remove it, God simply said, 'My grace is sufficient for you'. There will always be someone to talk to if you need help. Call on God, if He has control of your life, there is nothing He will not answer for you.
In closing, if you keep the faith, do your best (which everyone knows will not be perfect), study God's word, show the glorification of God in your works, deeds and actions, then you will have done the best you can do, and who can ask for anything more? God can't and neither can anyone else.