Doubts are normal. As other posters have said, write down your list of why you left...If you want, you can add to it a list of "No More"'s that you can now look forward to; I did this, with great joy I might add, when I realized that I was FREE of my husband's verbal and emotional abuse.
This is sort of what mine looked like:
No more walking on eggshells waiting for C to explode for every little thing.
No more listening to him rant and rave about how unfair the world is and how misunderstood he is
No more being yelled at and demeaned
No more listening to him stroke his own ego and talk about how great he is
No more picking up empty beer cans in the kitchen
No more taking said empty beer cans to the grocery store for refund because C has no more money to buy groceries.
No more cleaning up spills because C is shaking
No more listening to my stepson cry because his father drinks
No more pretending I want to have sex with a filthy stinking drunk
And so on and so forth