Practising bubble spots in an ICM calculator will increase your understanding of what a +$EV shove or call actually is. Just make sure to adjust based on player type once you find yourself at the table.
As a help to people, who have never worked with an ICM calculator, lets do just that. First we need to pick a tournament, and I went for a
pokerstars 90 man SnG, which is a nice example of a small MTT. 13 places pay, and 13 times the min-cash is around 29% of the price pool. This number is pretty normal for MTTs, so the "bubble pressure" in this event is pretty similar to most other MTTs. Each player start with 1.500 chips, so there are 135.000 chips in play.
To place us on the bubble, I put ICMizer into MTT mode and selected 14 players left, 7 on each table. I gave Hero and 9 other players an average stack of 9643 chips, two players a short stack and two players a big stack. I selected blinds of 600/300 with a 50 ante, which gives Hero and most other players a 16BB stack. Pretty normal for a bubble, that has dragged out a bit, because nobody wants to bust.
Hero now min-raise from CO and gets jammed on by SB, who also has an average stack. We press "ICMize", and the program now calculate the Nash equilibrium, which are the ranges, where neither player win or lose money. Or in other words the GTO ranges assuming, that Hero either min-raise or fold, and SB either jam or fold.
Those ranges are Hero opening 18%, SB jamming 20% and Hero calling 3,7%. Heros calling range is TT+ and AK. So its correct to call pretty tight here, but we are not folding everything, just because we dont want to be the bubble boy. We fold a hand as strong as AQ, but we dont fold QQ and certainly not KK or AA.
Now lets pretend, that the short stack on the other table got busted by an average stack, so that we are now down to 13 players and in the money. Still same 7 players on Heros table, still same stack sizes. Now the Nash equilibrium has Hero opening 26% of hands from CO, SB still jamming 20% and Hero now calling 8,4%. Heros calling range is now 77+, AT+, KQs.
So much wider than before, and Hero is also opening more hands to begin with. But its not like "LOL we are in the money, so now we can just get it in and gamble". We still need to open fairly tight, and we still need to mostly fold, when we get jammed on. Even a hand as strong as KQo is still a fold when jammed on.
I hope, this analysis was helpfull to OP or others. ICMizer gives everyone a free daily calculation for creating an account, so anyone can do this kind of analysis themselfes, which is a great way to increase your understanding of bubble or final table spots. Or you can purchase the program on a monthly basis, if you want to try it out without investing to much.