I find I work well under a certain amount of pressure.
It's when this pressure becomes too great (not having enough time to actually write the program, never mind thinking about it) when I start to crack. Sometimes this leads to MMM by getting more resource my way (when it's too late) although not always. Sometimes you just have to march on and get your scar.
It's retrospect where the process needs to be investigated and amended. Agreeing sensible amounts of work doesn't always happen for me.
There are so many variables and circumstances that not all PM's can forsee.. But again in my case, when it hits the fan, quality is out and JFDI is in.