When I was in my 30s, I remember chatting to a colleague over Friday evening drinks. (I confess, I cannot even remember her name). She was around 50, and commented on the fact I didn't have children. She shared with me that she had desperately wanted children in her late 30s and early 40s, and that it had tormented her that she couldn't.
But then she insisted that now, in her 50s, she was very happy without them, and in fact in many ways she was pleased that she never had children. In particular, she talked about how strong her relationship was, and how the freedom from focusing on raising children allowed her and her husband to focus on each other. Together their relationship was much stronger, and she was grateful for this every day.
Whilst I ignored her warning to ignore my biological clock (it was ticking loudly by then), I think the knowledge that she was happy, despite having dearly wanted children, helped me when it became apparent that we too could never have children.