Accept what you cannot control.
This single mindset shift will change the course of your life, saving you a lot of stress in the process.
And there's no need to sugar-coat it...
You cannot do anything about what you can't control. This includes everything that has happened in the past, and what happens in the future.
The only thing you can control is the present moment (which can influence the future), and how you react to what's in-front of you.
Yes, some things will sting. That's okay and I don't put anything past that. I'm not saying just click your fingers and get over everything bad.
What I am saying is, spending time stressing and allowing what you cannot control to influence you is simply damaging.
Focus on what you can control.
You cannot control the weather, but you can control what you do on a rainy day.
You cannot control how an examiner marks your test, but you can control how you sit the exam.
You cannot control other people's actions in any way shape or form, but you can control your own. (which can in-turn influence those around you)