Tips I’ve learned while keeping bettas with other fish

I’ve tried cohabitating some bettas with other fish a few times and I seem to notice a pattern. When my bettas were mostly aggressive toward another fish it was when they were new to the tank. The bettas I added into a tank that already had fish in it the bettas didn’t really attack the other fish. This is probably a territorial thing so I would always recommend adding your betta in aquariums that already have fish. I’m learning this the hard way lol