Most of us are optimistic about relationships; we want them to work because we have invested time, love and energy in them working. An abusive relationship is no different. What is different is that when you've been abused, your self-esteem and sense of self-worth can be seriously affected. This can leave you with small amounts of confidence to cope alone as well fears about what will happen if you are alone. It can also make you doubt whether you are worthy of happiness to a point that the relationship you know, even though it is abusive, feels comfortingly familiar.
All of these things can contribute to you returning. It is important to understand what motivates you to return and to give yourself time out of the relationship to work out what you really want with your life.