For me it comes down to asking the following questions:
- Did I read my opponent correctly?
- Did I get my money in good or did I bet into a better hand?
- Was the money going to go in regardless of the situation?
- Did villian make an incredible move?
It's extremelly important to understand what a bad beat truly is.
First example:
You get dealt KhKs in the BB, the BTN raises, you three bet, BTN calls. Flop comes AsKd5s. You bet, they raise, you push, they call. They show AdAc. Board runs out AhTs.
This is NOT a bad beat IMO. This is just really unlucky as my money went in behind, I probably didn't think the button had AA (although that would have been in their range), and the money's going in regardless.
Example 2: Same hand except villian has AcKc this time. Again, this is variance. Vilian thinks they are probably good on that flop with top two, and the river gets them aces full. Again, the money was probably going in regardless, but this time you got your money in good. Villian's move wasn't out of line - so you have to chalk this up to variance and know that if you do this again, next time (and many others) you'll win.
Example 3: This time let's say you have KhKd again, but the board comes 8d5c3s, and the same action happens. Villian flips over Ad8c, and hits an 8 on the river. Bad beat?
This one could be, but again my point is if you're getting your money in good - i.e. you're ahead, and you read your opponent correctly, you can't let one hand throw you. Poker variance happens and just because you're 85% to win on the turn, 15% of the time you're not. If this one hand happens to be in that 15%, guess what, %^% happens.
Playing poker is a marathon, a very long ironperson-like marathon. It's not a sprint. Don't let one hand kill your session. Learn from it. Pause playing, dissect it, see where you went wrong, and make notes on how not to do it in the future.