When we experience regret, we are choosing to replay our broken narrative over and over again. Our problem is that we take these failures on as our lost identity - the person we should have been. Then we torture ourselves with that idealized image.
With each passing year, we grow further away from what our ideal was, and we regret it. But the narrative is not necessarily true. The best is to let that narrative die. The older and wiser version of yourself knows what you actually want. Use it and move on.