Well i had this problem too for a long time even tho i have good results and a lot of final tables / 1st plc finishes in big field mtts.
everytime when i was going on a heater and had 2-1 to 3-1 chip lead over second with 30-20 left. i manged to blow it all in a few hnds late.
one of the major problem i had is how to deal with being moved to a table with at least 3 people deep stacked.
you know, normaly i pick on the shorter stacks but with a big stack behind i often ran my isolation into KK AA.
for example i have QQ in MP, UTG 1 is 30bb short and pushes all in, i shove 80bb while BB shoves with 70BB. obv i make the call just to find me in bad shape against BBs KK AA.
this leaves me with 10BB and i obv shove the next best AX into 99 TT JJ.
this happened to me in every second mtt i go deep in.
then i learned to avoid this crap you have to be very aware of chip management and RISK management late in tourneys.
while in the middle stages all that matters is to double up to get a confortable stack and you obv have to take big risks and this is all good, you have to know that in later stages your stack size is all that matters to get to the final table and make a good score or not.
i learned that if youre lets say 80 bb deep and you find yourself in described situation with QQ its better to just call the 30bb shove and fold to a shove that can actually hurt your stack and tourney life.
also important is of course how good your read is on the players at your table in this situation.
utg obv needs to double up and has a marginal hand most of the time.
but if BB seems solid and shoves, i would only call with KK AA in that spot. FK them queens. you can steal the blinds and antes 2 times after and youll have your stack back in controll even after folding that 30bb pot before.
also avoid to overplay AK AQ TT JJ in late stages.
only CALL these hands against small stacks and bet/shove these hands if youre at least middle or late position and there was no raise by a big stack before.
its been said a thousand times before and i can only recommend it to you;
patiens and discipline is the most important factor late.
let the agressive players bust each other and climb up the ladder in price money wich also is a psycological factor and gets me more confortable knowing i have 5x my buy in guaranteed already and i dont have to stress nothing.
with so many antes and blinds out all you really need is just one premium hand to hold up late and youre guaranteed a top 3 finish.
i often used to overvalue the chip lead aspect, you know..
"if i call this guys shove with a even stack and win with my JJ i will have the chiplead and will win the tournament" ..
thats just not true and for me personal the risk management comes to play in this situation more importanat then everything.
even if i have QQ and the odds / ev normally would be standart, i just dont have to call his shove because im not at middle stage anymore, im running for the FT and this call would end my tourney or cryple my stack.
and 85% of the time does (not to mention if theres another player in the pot, this would reduce my winning chances a lot more and i think the fold even easyer).
i dont know if this will help you but when i realized that i get to nervous on the run for the FT i sometimes sit out in a few other games and concentrate more on the mtt im deep in. this makes standart plays not so standart anymore and i can focus on the other players as well and most important get a feel for the table.
so i hope i wrote my thoughts understandable (since im not so good in english) and maybe there is something that gives you a inspiration on your later stages mtt game.
BTW: the whole dynamic changes when youre on the FT....obv