It really depends how philosophical you are, and who you are.
I know a mum who told me if she could go back she wouldn't bother with kids, that the things she has learned are not really worth knowing. She misses her freedom, and although I know she loves them and is caring, she has no problem telling me these things in confidence. She is disappointed in them, and doesn't have the energy to make them behave better, or create quality time.

Sometimes I feel like banging my head on the wall and I know I yell a lot more than I should, but even in the darkest moments I wouldn't change a thing. I understand so much more about the world, about people and relationships. My contraception failed, and I was never taken with kids before, but when they are your own it's a lot easier to cope. I still have very little tolerance with other people's kids.

The first thing I noticed was whenever I heard a sad story involving a child, or saw a dying child at work it made me cry, I could grasp the parent's pain, understand the weight of the burden on a mother who has to find food for her starving child in a third world country.
It definitely made me more aware.

I don't see it as self destruction as by it's very nature having children is the continuation of your genes, and it's not a life sentence. They grow up, leave. If you have brought them up to be independent they won't be a burden, and although there may still be a lot of worry, it's still worth it.
I have cared for elderly who haven't any children, and when everyone else has their grandchildren visiting, and their children to come round and help them put up shelves, do the garden, etc, all they have is free time, memories. Maybe a lot fo experiences in their lives, but not the same depth of love that comes from such a close blood link.
If you put the effort in to bring up a child well the rewards are huge, but if it's something you really don't want, although it may turn out fine, it may not.
Some people are just not natural parents