Playing in the deep stages of MTTs is something that a lot of players struggle with, especially those playing lower stakes.  A lot of players tend to get too nitty at these stages, for differnt reasons(sometimes people fall victim to both).  The main two I find are; Scared to lose a significant portion of their stack, or afraid the smaller stacks will shove if they open light.

In regards to the first of being afraid to lose some of your chips, this usually stems from people who dont put ina  lot of volume.  When they actually get deep in a alrge field tourney they realize this doesnt happen a lot, and start to play as 'scared money'.  To overcome this, besides increasing volume, you have to actively pressure yourself to make the best choices. Realize that you may be afraid to go bust this close to the major money, and overcome that by realizing your chance of getting to the major money INCREASES if you open up a little more.  Look for spots to steal, pay attention to who folds their blinds and who doesnt, you see somone opening a lot?  if you have played a lot of hands recently 3 bet them, put pressure on them, a lot of times they just want to take it down pre or with a small cbet post.  It also helps if you have noticed this person fols to 3 bets.

In regards to the second, a simple understanding of the math would help.  Heres a generic example.  lets say it folds to you in the HJ. There are 4 people behind all standard tags with 15 BBs, you dont expect anybody to flat, so its either shove or fold.  Lets say their shvoe range is as follows: 22+ ATo+ AJs+ KQ. This is 12.2% of hands.  So the chance they fold is 87.8.  So the chance they all fold is .878^4 or 59.4%.  so almost 60% of the time they all just fold, and what do you pick up? Well assuming its a full 9 handed table and antes summ to 1 BB, we are looking at 2.5 BBs(1 BB + antes+ SB).  So if we raise less than 2.5BB we are making chips EASILY…and heres the kicker, WE STILL WIN CHIPS IF WE FOLD TO 100% OF THEIR SHOVES.  Which means we can open ATC to 2.2 BBs here and fold 100% of the time to shoves(even folding aces in this hypothetical) and STILL TURN A PROFIT.  Obviously if you are raising ATC 100% of the time in this spot, people will start to shove lighter, meaning its no longer profitable, and there is also the problem with people calling, but you can still show the math that even if you give up 100% of the time post flop(even if you flop the nuts), you can still turn a profit in a lot of scenarios.

Now I am not going to go into more depth in regards to what you can get away with, jsut think about that spot in aprticualr and realize just how little people actually have hands they are willing to commit for their tournament life.

One of the biggest differences between Great late game players and mediocre ones, is the willingness to gamble.  the great players know they will be back, so they may 4 bet shove JTs in some spots, they are not afraid of busting this one, they will take every +EV spot they can.  Mediocre late game players will steal a lot but will often fold to the slightest sign of resistence.  This is something people get better at with experience and volume, but it also takes a certain level of concious effort to strive to notice and captialize on spots without fear.