It's a vicious cycle.
As long as I was high I felt no guilt. Meth makes everything seem better - at first. I didn't realize how terribly I was neglecting my children. I didn't realize how traumatizing it was for them to live in domestic hell. Then I would come down. Coming down from meth is a terrible, depressing, mentally agonizing experience. The guilt I would feel after returning, sort of, back to my senses was unbearable. I would swear "never again" only to know that everything would be better, the depression and guilt would go away once I would use again.
Then I quit, finally, after many many attempts and the guilt began running a new cycle. Depression fed the guilt, feeling more guilty fed the depression. I would think "what a horrible mother I was" and the guilt would build and the depression would become unbearable. Then I would think "I am still stealing time away from them by being so depressed" which would then in turn into another thing to feel guilty about. Where once my children had reprise from the constantly depressed mother with brief periods of happiness and attention, between violent psychotic episodes and fits of depression, now there was none - just never ending (or so it seemed) bad days. It wasn't fair to them and I knew it which also led to continuing guilt.
Eventually, as my mind healed, the depression started to lift. I finally began to understand that I needed to replace the depression with determination or nothing was going to get better. Forgiving myself was and is so much harder than forgiving others. I still haven't forgiven myself and have came to terms that I might never reach that point, but at least I can live with myself now.
Depression and guilt are normal for recovering addicts. Accept that, but don't get trapped in it. It will get better. Our children deserve better and they will get it as long as you don't give up. Time does heal.