No matter how you live your youth, you will probably regret it when you are older. Unless you inherit so much money that you don't have to ever work in your life.
If you spend your youth having fun and enjoying your youth, then when you get to middle age you'll have wished you worked harder and saved more so you could be wealthy and comfortable.
If you work your butt off in your youth and have lots of money and successful career, you'll wish you spent more time relaxing and having fun in your youth.
The key is finding a good balance between working hard and playing hard. Your career won't suffer if you take a week long vacation. Your health will be fine if you sometimes volunteer to do a weekend shift. Do both and you can be successful and happy about how you spent your youth.
As an American, this is a very American answer, and I wish I could disagree.
Oh, and wear sunscreen.