You can go to bed every night and know that you've done a good job. First, be gentle with yourself. You do not need to be anywhere near perfect to be a good mother. In fact, I suggest that if you think you're perfect you are not doing a good job. Focus on the positive aspects of the day. Forgive yourself for the less than positive ones.
When you go to bed tell yourself that you're a good mother. Push aside the self-criticisms and focus on what went right.
At another time, not at bed time, think about the situations that were troublesome and decide how you could handle them differently. In this way you continue to grow as a mother while recognizing that you are doing the best that you can. That is all that's required.
Bruno Bettleheim wrote a book entitled The Good Enough Mother. Just knowing the title helped me to not be so hard on myself. Reading parts of the book helped me recognize that just by being my child's mother I'm ahead of the game.
BTW families on SuperNanny are in a desperate situation. You would not qualify. Just as MzKitty, I get a lot of good ideas from watching the program. In fact I would put that program right up there with the books I've read as far as being helpful.
I agree that it would be great to have a trained person help us. I've found that going to counseling has helped me be a better parent and grandparent.