Was making huge progress with God... hit a brick wall. Is this the enemy?

I have been studying the word everyday, some day's in excess of 12 hours. I can't get enough because I "thought" things were starting to make sense, and I've learned things I could have never imagined. There was a light that came on and a peace I have never felt. I was always quick to say I had read the Bible, however this is the first time I have actually studied the word. But yesterday I read a post that left me feeling "in the dark again". Is this the enemy or for a lack of a better term "am I fooling myself"? I've failed in so many ways, can God use me, does God love me...or have I failed "too" many times?
Debbie