The thing I (eventually) realized was that all that advice and techniques almost never help with the current situation you are in. However, it almost always helps with future situations. Rarely do kids (or people, or pets even!) stop their reaction when you use some technique. However, the next time they have that reaction, they will remember what happened before and react differently.
So when my son was a toddler and through his food on the floor, me taking the food away caused a tantrum and made that moment worse. However, the next day (or whatever) when he had the same food, it was much less likely he would throw it on the ground because you could see him remembering what had happened before.
I think of it as teaching my future kid ;)
And so far, it still holds up (my son is 10). If he is arguing too much with his friends, the discussions I have with him about it rarely fix the immediate problem, but I can see it have an impact on future situations. "Dad, my friends were being mean to me, but I remembered we talked about how sometime I talk over them, so I stopped talking as much and they started being nice to me again." Stuff like that.
Also: parenting is fucking hard, I agree, and 100000% agree on being empathetic with them. By far the biggest phrase I use that helps with my son is, "Buddy, growing up can be really tough, and we're here to help as much as we can!"