When you generally hear this phrase it’s in reference to someone who is possibly middle aged and suddenly feels like they are a teenager again. This can be good because you have a lot freedom and no responsibility but it can also be very bad because although you have energy you don’t have experience or money. You haven’t made the decisions yet that allowed you to grow. The events that caused that progress are yet to happen.
In my case at 17 I was reset to a new born so that wasn’t a pleasant experience. It was bad enough the first time but to go through it all again has been quite painful.
I lived my life closeted with few interactions with others. I gained knowledge and an appreciation of history, nature and science fiction but no understanding of people in general.
Now I have experienced what I expect others did with parties, friends and alcohol.
I’m not sure which is the better route to take in your teens. I think a bit of both probably is but it’s difficult to mix one with the other. I tried my best. I’m still learning who I am and how to be the best version of myself. To have lived one life with the eccentricity of an undiagnosed autistic that just floated through life as there was never a goal and nothing truly interested me to one of a diagnosed autistic that didn’t have my previous mathematical or organisational skills so I could no longer program or perhaps become interested in physics has been extraordinarily difficult. Add in the hormones which were not present before and you have quite the melting pot!