What it boils down to is each and everyone's abilities, but more so, each and everyone's proper judgement of their abilities!!!
My in laws keep thinking there isn't ANYTHING I can't do - a nice thing for someone to think of you, however, the way I see it is they just haven't asked me to do something I'm unable to do - a VERY BIG DIFFERENCE!
Deciding whether or not to build my own pool was a daunting task at first, once I looked it all over, the hardest part seemed to be getting the liner in right - to this day, I feel that it still is the hardest part of the job - getting something level isn't hard given the right tools, setting up the wall isn't hard - it's somewhat physically demanding, but not hard, installing the equipment - probably the easiest part of the job for me because I like messing with mechanical stuff.