Lame title? It sounds more interesting than "preconceived notions."
One of the biggest limiting factors I noticed people have is the notions they cling to. While it's not totally wrong, there's a big loss on not seeing what you're missing out on.
Enter the aforementioned preconceived notions.
If you assume or rigidly adhere to a certain thought - such as long distance running is superior for fat loss - then you're not making the best of your time. So stepping out of the comfort zone is necessary once in a while to see if you're missing out on anything.
I'm all about efficiency in training so I do what I can to make sure I get the most done while I exercise. The simplest asset at everyone's disposal is that huge squishy brain we all have.
Mindfulness and being attentive are trump cards in the quality of an exercise session. Gauging you're movements and smoothing out the kinks is what it's all about. Time melts away and you're pretty much in the zone.
Likewise, exercise is only as difficult as you perceive it to be. If you think it's going to be gruelingly long, drawn out, horrible, and just a way to torture yourself, well guess what? It's going to suck, a lot.
Now, how do we make use of something that is making life crappy?
As simple as it sounds, think the opposite. Get a good feel for how your session really will be and map it out entirely in your mind. Be realistic and then envision going a little past what you're capable of. (check out "Mental Boost for Better lifts here)
The brain sends commands to your body and it's the conductor of everything.
It's your job to control it.