Looking for some advanced advice/strategy dealing with stacks around 25-50BB.

Notice I'm offfften one of the chip leaders throughout the first half of a tournament, and too often sort of fizzle out. Can only equate to a poor middle game. and/or late game.

Of course I know all the essentials, reshoving sizes, stacks to avoid raising, stacks to pick on (3-betting 25-30ish realm bb), etc, etc..

Any good recommendations to step it up to next level for midgame/late game specifically? Could be variance but seems like quite a number of tournaments I'm bubbling out or min cashing whereas I had overall chiplead or in the top few spots half way through it...

Thanks !