Let us try to understand this clearly, shall we?
Let us observe two cases:
1... I want something; I try to get it; I fail; so I am disappointed.
2... Some things, I can never get/change; so I am disappointed.
What is the difference between the two cases?
In the first case, there is still a chance. Yes, failure has disappointed me, but it has not killed me. I could whine and cuss, blaming myself and others all my life, but I know better than that. Have I taken the time to ask "WHY" I failed? Now it boils down to how I handle failure.
Failure teaches very valuable lessons. The question is not whether one is willing to learn from failure or not. The question is whether one is afraid of failure or not. Fear is an ultimate driving force. For some of us, fear of failure is a great motivator. One who is afraid of failure will take all possible measures to avoid it. Ones knowledge dictates what the measures are. What if one fails even after doing practically everything in ones powers not to? Then, one automatically learns the new reason that made the failure possible. And if one is afraid of failure, one will consider this newfound knowledge while planning the next attempt. Knowing that, I would be good to myself. I would not put myself in a coffin and nail it shut.
In the second case, there is simply no chance. I should accept it. For instance, I cannot become younger by 10 years again.
It is good that I cannot, because time has given me experience and maturity, which I am not willing to relinquish. I have just one simple prayer for such conditions - "God give me strength to endure that which I cannot change."