The problem posed by OP here is at the crux of the successful jump to higher levels in tournament poker.
I will venture an educated guess that we all go through this, continually! We are human, and it is nearly impossible to to avoid that feeling of invincibility we all get when things start off well. Nearly impossible, but not absolutely impossible.
I know I struggle with it EVERY SINGLE TOURNEY I PLAY. It is a major reason I have always preferred HORSE tourneys. The changing games prevents me from falling into a rut. On those occasions where I show myself I have the right stuff and can avoid just playing hands because I have the big stack, I find I do much better. But during the middle stages of all MTT's we all suffer with some sort of anxiousness. Could be we don't think our big stack is big enough, or that we remember reading somewhere that as the big stack there are some fuzzy responsibilities involved to use that big stack like a club (nonsense for the most part), or in my personal case I get that feeling I need to be the Table Cop.
Proper poker can be extremely boring. They call it the grind for good reason. I almost always have some other distraction going during play, usually solitaire. Time dependent distractions like a significant other demanding time right now, or a side game like tetris don't work well. But solitaire is not time dependent.
Many folks deal with this by multi-tabling.
Perhaps the bottom line is yeah, you do increase your opportunities when you start well, but you (and I and everyone) need to remember that a 1% or 5% increase in steal attempts will suffice. You don't want to go hog-wild and steal every other hand. That for sure will end up pokercidal.
