When I was a kid, I asked teachers and anyone else I perceived as an authority figure if they knew why I reacted emotionally the way I did. I literally did not understand myself and was asking for help, and adults knew everything, right?
I understand what you're going through, and I know a lot of other people on this forum do. You have our understanding, sympathy, and empathy.
Counseling from someone who understands autism would be great, if it's available. Here are some things I've learned from my own experience:
1) The standard strategies and behaviors that work for most other people aren't going to work for you. You already know this, and you're frustrated from trying them. You are going to have to figure out what works for you. You're going to have to write your own Owner's Manual.
Start with the things that set you off - look for what they have in common. Is it having too many things to process at once? Is it noise? Is it sudden or unexpected change? Is it not having time to prepare for a situation, or not having time to process something afterward?
Once you know what sets you off, there are two basic strategies:
A) Ways to prevent them.
B) Ways to deal with them.
For ways to prevent them, look for things you can do to prepare in advance for what sets you off. Maybe that's rehearsing and scripting responses, planning your schedule ahead of time, planning for things going wrong, etc. The best thing for me is to make sure I get enough sleep. Look for things that weaken you and make you more prone to meltdowns.
For ways to deal with them, pay attention to how long it takes you to recover. In the moment of a meltdown, this will help you to know that after [that much time], you will feel better. Also learn to recognize when you are heading for a breakdown, and remember that your thoughts at the time are going to be darker than reality really is. Look for activities and things that soothe you and help you recover, and prepare to have them ready when needed.
That's a start. Understanding yourself, learning to cope, and learning to change is a big project. It's going to take time. You wouldn't get mad at a toddler for falling down when they're trying to learn to walk - be just as forgiving to yourself.
