I used to play semi-pro a couple decades ago when Poker was having its hey day. Won a few modest tournaments. Played a lot of high stakes limit poker and no-limit. Limit poker is a little more mechanical, and the most you can lose in a pot is limited to the bet size though with several players your position matters a lot since you can get raised in front of you and behind you if you don’t get the other players to fold. No limit, well, you can bet any amount at any point which makes it scarier when faced with a big bet decision.
Today the game is tougher. Cash games are truth or dare. Tournament games are as much about not getting knocked out out of the tournament as they are accumulating chips. So tournaments are about saving chips as much as winning chips. Reading your opponents’ playing style and figuring out which kinds of hands they are likely to raise or call with, and then reading the board to see if those hands are likely to have hit or miss or give him/her a drawing chance. Which of course means opponents have to vary their starting hands and style a bit just to make them harder to read over the long haul. A lot of bluffing and semi-bluffing due to that psychology.
I read a book by a guy who was a PhD mathematician who made a living for a while playing on-line poker. He said when he first got into it, it was easy pickings, there were a lot of terrible players, suckers, throwing away money. But over time, the suckers got tired of losing and the sharks were playing each other. It got harder and harder to win and eventually, he started losing and dropped out. It went from easy money and better than a paycheck to a dry hole in about year.