I was 23 and my wife was 25 when I got married. No, I was not ready. I didn't know myself well enough. Like others, I'm still learning about myself.
I sort of have mixed feelings about it. I know now that I have no interest in marriage. But as with many things in my life, I value the experience. I regret many non-actions, but I rarely regret actions that I did take, opportunities that I did pursue, even if the outcome wasn't what I wanted or expected. At least I tried it and I know and I don't have to wonder, what if. On the other hand, if I had waited, I probably would have figured out that I don't want marriage in my life without hurting someone. Getting married isn't really something you should try out considering the feelings and high risk involved (not that I felt I was trying it out at the time. I felt very serious about it.). Maybe people can try shacking up. Further, part of the reason I am still learning about myself is because I got married as a Jehovah's Witness. I'm 30 years old and I've done about as much dating as a 16 year old. When I got married, I was burying my true self under JW indoctrination.
The ironic thing is that as a teenager, I always thought to myself that I would not think about getting married till I was 30. But here I am 30 and I've already tried it and lost interest. If only I had kept to the original plan. Ah, there's a "what if" scenario for a non-action.