I've had too much advice, too much knowledge, to possibly put it down to one thing.
@Sighs point is accurate though... if you really need one point.
Think about any bad day, then think about how you've had a good day after that day or period... which proved it will pass.
The best advice I ever got was: If you want to heal your trauma, then it's going to hurt you more healing it than when you went through it, but you will get through it.
That was the best advice I ever got, and that was from my therapist who was a little old lady, an ex war widow, and who did nothing but help combat veterans for decades x times per week. There is no easy option, even suicide is difficult, because you not only have to do it, all your loved ones are left to pick up the pieces. There is no easy option through trauma, it doesn't exist, and you have to prepare yourself for a lot of short-term pain in order to get through it, for the long-term gain you achieve by healing trauma and working on managing your symptoms.
I've helped people through complex trauma, who some of the worlds experts had written off as untreatable, to help themselves and adopt that approach. They are no longer here for the most part, and back in life to some degree... with far less symptoms and happier daily lives. In other words, nothing is forever and you can get through trauma with a lot of hard work.