Why not both?

You don't dwell on your mistakes in life, you learn from them. You can't change the past, but you can change and influence the decisions you make in your future. Like the saying goes, life is 10% of what happens to you and 90% how you react to it.

Both is certainly an option, but most people lean one way or another. Some people find more wealth in reflection and some find more success in never looking back. You can tell when someone never learns from their mistakes, but you can also tell when someone is stuck dwelling in the past. Very rarely have I ever encountered someone who is balanced and does both well, or even both at all. The ideal would be both, but its a hard mindset to have

I use a time machine to reflect on my future