There are two types of all in players, and t's very useful to distinguish between them, They are seperated by the number of time they are all in, The player who is all in a lot is trying to do a number on you by frightening you out of the pot, using the psychology of your fear of getting knocked out. If you get a good hand call their bluff. The seldom all in player on the other hand has a rock solid hand and it's better to muck.
This is true, but it’s not always quite so simple. I’m generally a tight player, but in a recent sit n go, I all in bluffed as I was short stacked. My opponent folded, probably appreciating I’m usually tight. Next hand I went all in on the flop with a set of aces. My opponent now thinking I was a bluffer, called and I busted him out.