Spiritual discipline

Why is it so hard to be spiritually disciplined? Certainly it's because man is fallen. And maybe it's because being disciplined is hard anyway. I was thinking about this the other day and came to the conclusion that if I can be disciplined to run 3 times a week, then surely I can discipline myself to keep my house clean or spend time with God in His word and in prayer. Yet, it doesn't happen that way. I prayed the other night that I would be woken up early to spend time with God before all the goings on of the day got started and I got too distracted to spend good, quality time reading my Bible and praying. God answers prayers. I'm not so good at the follow-through, though. Yesterday, He woke me at 7:10. I got up and then crawled back into bed for another hour and a half of sleep. Today, it was 6:10. I got up and once again crawled back into bed for almost 2 more hours of sleep. Why is it so hard for me to be faithful in this? He wakes me up early when I ask for it and then I don't follow through. Why is He still so faithful to me when I don't hold up my end? Why does He love me so much that He keeps answering prayers and being faithful to me. Evidently I love sleep more than I love my God. But, He is faithful and will continue to be faithful even when I fail Him.