A couple of years ago, I was complaining to a family member about a frustrating situation that I couldn’t get over.
About halfway through my complaining, this family member played “Let It Go” from the Disney film Frozen and we both burst into laughter.
All jokes aside, the exchange offered a valuable lesson that I try to be mindful of to this day: sometimes the best thing to do when we’re frustrated — no matter how justified our frustration may seem — is to let it go.
Your energy is almost always better spent elsewhere.
By understanding why you grabbed it in the first place and why you are holding on still.
Setting aside time to focus on your breathing, notice when you're getting distracted, and gently bringing your attention back to your breath helps train you to recognize thoughts as ephemeral appearances in consciousness.
The more attuned you are to this perspective, the easier it is to recognize just how short the half-life is of any experience. You can literally be angry in one moment and fine the next.
The book The Happiness Trap covers this. There's a difference between identifying with a thought (you can be on that bandwagon for awhile) and recognizing that you're identifying with one (easier to get off).
Ironically, it seems most helpful to just welcome whatever disturbing thoughts or emotions you're having than to actively try to suppress them. If anything, the latter amplifies.