There may one day be a person, or perhaps several people, who will comment on a failure on your part to accomplish something, or maybe just falling short of achieving some long sought after goal with the words, "Forget about it kid, you have your whole life ahead of you."
Ignore that person or persons. Those people are pure poison to those who wish to succeed on a high level. Start associating with people who, in the exact same circumstances say the words, "Don't let that set you back. Figure out what you did wrong and then try again, eliminating whatever mistakes you made."
Hell, surround yourself with those people. Those are the people who understand failure is just a lesson to be learned and then applied, Those people who tell you to quit while you're ahead, who say you have your whole life ahead of you, they are wrong.
There are no guarantees. The only thing you have ahead of you is the next moment, Tomorrow may ever come. If you keep quitting every time someone makes a disparaging or discouraging comment regarding your efforts, you may soon find yourself saddled with too much doubt to ever try to pursue your ambitions again.
Do what it is you want to do, and do it to the best of your ability.
Unless what you want to do involves hurting or taking advantage of other people, Don't do that to the best of your ability - Don't do that at all.