I go through the same doubts, I separated from my husband in August. It has gotten better over time, especially as I have seen the ways in which my life and my children's lives have improved. I keep going back to a quote I see here frequently and it really helps me:
"If nothing changes, nothing changes."
My husband is not going to change, therefore if I no longer wish to live with screaming, yelling, holes punched in walls, slammed doors and a house full of anxious children & animals, then I need to make a change. Otherwise, the rest of my life will be exactly like the last 9 years.