Struggles

So I get soooo frustrated at times with myself. I seem to struggle with the same set of sins over and over again. Each time I go back to God and say, "You and I have been here before many times but I still need to ask for forgiveness for this same sin." Sometimes I wonder why God is so willing to forgive me when I so easily fall back into the same sin. I know God has forgiven me and I am soooo thankful for that but sometimes my mind can't comprehend why he does when I continue to commit the same sins (although I don't mean to).