About 6 years ago, I went to the hospital to visit a friend who'd just given birth. Another friend L, who I hadn't seen since high school was there too. I don't remember how it happened but L, who was also married with children, wound up giving me unwanted advice in a wagging finger tone about how I should think about having kids young "because it's better". I was single at the time and was smarting from a recent breakup so...well, I immediately lost my cool. Ahem.
(I'm mildly horrified thinking about it now, but I think the friend who'd just given birth had to intervene and calm me down.*)
That was 6 years ago. Now that I'm married with a baby myself, I look back and realised that it's true. It is better to start young. But I would never say that to any of my single friends. I'd say it to married friends wanting to put off having children. But I would never ever say it to my single friends. I've been there and it really hurts to hear it.
But back to starting young. People may not like to hear this but parenthood is a young person's game, it really is. It takes energy, actual physical flexibility and a strong back. Plus, okay even if you argue that "it will keep you young" and "you feel fit and young", chances are, your eggs and sperm aren't actually young. Lots of very young looking people wind up having trouble conceiving because even if they look 25, their ovaries and eggs are still 40. There are lots of things you can run away from, but I've learnt that it's really hard to run away from your own biology.
Now I look at my friends who married in their twenties and had kids with a certain amount of envy. They have older children to help with the younger ones, plus they're done with childbearing whereas I'm only just getting started (I hope!).
*I have really wonderful and understanding friends.