Editor’s note: This isQuoraAn interesting question. Here are the answers with the most upvotes.

1. I would not date anyone. It was a total waste of time.

2. Work on getting better at skills important to sustain in life and become successful.

3. I'd excercise and work out to feel more healthy.

4. I'd not try cigarettes.

5. I'd be more organized.

6. I'd start saving money.

7. I'd be nice to each and every person and keep my ego aside.

8. I’d start reading books and improve how I write.

9. I'd learn how to cook and eat healthy.

All of the above are things I realized now when I'm 25. I know it's not been long since I was 20 but I always feel like I wasted so much of my time.