Stickwithit yours is one of the most practical and sensible posts about this I think. You have to have an awareness of what makes you happy before you can look for it. It's quite sad reading the posts on this thread, many people seem to have woken up in the wrong life, somehow. But how did that happen? How can you go so off-course and not really notice?
I don't have it cracked, but what I do notice is that my friends who are happiest with their lot are those who have quite similar lives to before they had children. So, I still wear make-up and clothes I like (I look like me, in other words), go out to dinner with my husband (babysitter or family babysitting), do a similar job (which I find interesting) and have all my old friends from years ago (so phone them, have meet-ups, generally prioritise friendships where I can).
The friends I have who have struggled the most lost their identities when they embraced motherhood, and often put massive pressure on themselves to be the perfect homemaker/co-sleeping/earth mother. For one or two, this was a great fit and they have loved it, but for several more, it just wasn't them. They now find themselves stuck at home a lot or doing rather unintellectually stimulating jobs and wondering if this is it. I also notice that the friends who went full-out for the motherhood ideal dropped a lot of old friends or just don't prioritise friendships, now they feel lonely as they have a few new mummy friends but these aren't the deep friendships they had in the past.
I think it's important for mothers to reconnect with their own identity (which presumably you had a bit before motherhood), look like themselves and do the things which they like to do. It sounds very selfish, but actually, if you look at a lot of husbands, they do their hobbies, they dress how it suits them, and they often work in jobs which make them feel important (even if they are not:)) I also think keeping a connection with old friends is important, as they know who you were before you had children. I think if there's a massive disconnect between your past and your present with children, it can make you resent the children, whereas I feel like the same person I always was, with a couple of kids in tow, it's a different feeling.