Ask yourself what's stressing yourself out, but figure out why it's stressing you out. Once you do that, you can actually figure out an effective way to deal with it.
For example, say you get passed up for a promotion at work you wanted. At the surface, you might think, "That guy/gal who got it is far shittier at their job than I am," and some people would leave it at that and either publicly or privately take the piss out of that person. All that does is reinforce negative attitudes and slings mud at someone who, for all intents and purposes, might have actually deserved that promotion.
Stop and think why you're pissed you didn't get the promotion. After a moment you might realize... Yeah, you're not entirely mad at that person. You're mad you didn't get the promotion. Why? Cause you worked hard for it... Certainly. As would anyone. Go deeper. Why are you stressing yourself out about this? Cause you really want to be respected by your peers? Feel any clearer? No? Okay, that's probably not it then. Keep going... Cause you feel like you just wasted x-amount of years? Did you just feel your head clear up and your shoulders feel lighter? Okay, then that's why. Now it's time to take stock in what you did in your time as an employee and see... You know what? You learned a shitload. Regardless if you got that promotion or not, you still got some really good experience out of it. And, you know what? Maybe you did slack off here and there. If you're serious about what you want, you now understand where you went wrong. But, in order to be clear and objective, you gotta ask yourself those basic, root questions, and importantly: BE HONEST WITH YOURSELF. You don't gotta lie. This is an open dialogue with yourself. No one else needs to hear this shit.
I generally think that's why I hear people complain about the same thing ad nauseum... It's not that anything has changed, they still haven't figured out why that particular thing pisses them off, and are just repeating the same info to parse out clues. I think talking to other people can definitely help, but only you know the full story from your perspective. As such, you can be an effective stop to making yourself feel better.
So, yeah, that's a wall of text that sounds self-helpish... but, genuinely, doing shit like that has gotten me through some pretty rough patches. Whatever piece of advice you go with on this thread, hope you feel better!