A recent post in the forums got me thinking about this concept again.  In the post, the OP complains that they flopped the 2nd nuts and lost the hand.  It was simply a bad beat complaint out of frustration, but it brings to light a fundamental point about improving your poker game.  In order to grow beyond this limiting mindset, you have to think in terms of hand equities.  Once you do, you’ll understand situations much more accurately, and also find that you tilt less as a result, which is always a good thing. 
The OP in the hand actually didn’t flop the 2nd nuts, they flopped the 3rd nuts, holding 77 on a 7JJ board.  They had 2 opponents both stacking off on the flop with them, likely that at least one holds a J.  In fact in this case both did, they held KJs and JTs.  The OP was on a short stack and both opponents covered, so they got the money in with a chance to triple up.  This was a fantastic situation for our hero!  But it was far from a bad beat.  In the hand our hero actually had about 68% equity on the flop.  If we could continually get our chips in with a 2/3rds equity share of the pot, getting a 2-1 overlay on our wager to boot, we would have long term results beyond the best in the game.  But on the way to those results, over thousands of trials, we would lose some of those pots.  To put it more succinctly, over 1000 such times we would get drawn out on roughly 320 times on average.  That’s a lot of losing trials.  By reviewing the situation in terms of equities, we can much more easily absorb a single losing trial with a level head and understanding, and be much less likely to tilt from it.   When we think about it as though we flopped the 2nd (or 3rd) nuts, got our money in good, and got drawn out on, we’re much more prone to falling into the misconception that the deck must be stacked against us, we run terrible, and a host of other negative, self-destructive thoughts that can lead to poor decisions and more bad results.

To help illustrate the point, let’s take an extreme example.  Let’s say you hold 6d7d in a multiway pot, and the flop comes down 5h8c9c.  You’ve flopped the nuts.  Obviously this is a great spot and we’d be happy to get all the money it, even multi-way.   But depending on what our opponents hold, it may not be as great as you think, and in fact in the worst case scenario it could be a disaster.  For example:
Flop:  5h8c9c
You:  6d7d
Player 1:  9s9d
Player 2: JhTh
Player 3: QcJc
Player 4: 6s7s
In this disaster scenario, we are splitting the pot with player 4 when we hold up, and the opponents have just about maximum outs collectively to draw out on us as well.  Our equity (share of the pot) is only about 8%, which is a pretty bad return considering we will contribute 20% of the pot from our chip stack.  Getting our money in this bad over and over again will find us getting broke rather quickly.  And yet, we flopped the nuts.
Usually when we flop a very strong hand, we will be getting money in very good vs. an opponent’s range of hands when they are giving action.  And when we win those hands it goes largely unnoticed by our conscious brain… we were supposed to win after all, we flopped a monster.   But it’s a very rare situation indeed where we are 100% to win on the flop.  By reviewing situations in terms of equity, we can better identify the true bad beats (yes they still happen) vs just the more standard spots where we are simply getting the best of it but are in a far from unbeatable spot.  And a better understanding of these spots + less tilting, is going to lead to better results in the long run.