Because he's telling you that your time is over

No my time haven't gone yet. In fact that's the time when everybody make up its own story about the past
People tend to create stories about their past which the others will like. Because past is mostly hardwork, a lots of troubles you went through, a lots of negative experiences, a lots of mistakes and failures.

No my time won't be gone yet even when I'll reach your age. In fact, I've seen all of your mistakes, and I won't repeat them. I'm ahead of you for few years and that's competitive benefit, I can reuise my time, repeat it, while the biggest disappontment for you is that you won't be able to see the way I'll live in your ages. Maybe its better because it will be hard: since the level of life quality will be way higher.

He's envy.
Because his time is over.

Fight jealousy. Because the same mistake can happen to you in future.