We've all had our disappointments. The loss of a job, the disintegration of a romance, the fading of a friendship, etc. But "disappointment" isn't fatal. You can live with it...
Chances are you've already worked your way thru the stages of sadness, anger, denial, etc. to reach "disappointment". The good thing about it is a certain state of "acceptance". Hopefully you've done the best you could at the time and learned from the experience. Can you move on and let go? The key becomes being grateful for what you do have and not let the disappointments overwhelm...it's a battle...
Here's 5 songs on the theme:
Neil Young "Mr Disappointment'
XTC "The Disappointed"
Bob Mould "Disappointed"
John Lydon once sang that "Anger is an Energy" and it can be for a short period of time. If it lingers too long it starts to eat at your soul.
Public Image Limited "Disappointed"
Boston "Used to Bad News"