I don't get it

Why does everything have to turn out more difficult than you thought it was going to be?
ESPECIALLY home repair.
And I know I can't tell a socket wrench from a circular saw; "Lefty-loosey, righty-tighty" is just doggerel to me cuz I have a hard time with concepts like left and right; so I expect home repair to be difficult, but DAMN!
I have spent my entire Saturday trying to put a piece of rubber on the bottom of my garage door, so that when it rains (as it seems to just about every day lately) the garage won't flood and seep into my office. I sit here 48 dollars poorer and with no rubber on my garage door -- no metal either -- carpal tunnel from drilling through aluminum (what numbskull called this stuff "soft metal?) and praying it doesn't rain.
I started out by cutting a piece of the rubber under-the-garage-door stuff I need, cuz I don't speak hardware and I don't know what it's called, but at the hardware store they just look at my doohickey and say "Where did you get this?" and I have to say it's an under-the-garage-door-rubber thing, and they have something sort of like that, but it's for wooden doors, is your door wooden? A quick surreptitious phone call home lets me know that my door is metal. (And yes, I know I should have noticed some time during the seven years I've lived here; I told you I was bad at this.)
At the big home improvement store all the way across town they have lots of garage door rubber stuff, but nobody will talk to me, and I just buy the most expensive thing they have -- which may not sound economically foolish but is actually a frugal move on my part; past experience has taught me that only the most expensive thing has a chance of working and it's cheaper to just buy that right off the bat than buy something cheaper and then have to come back for the pricier piece.
(Pretty shrewd, huh?)
Back home, of course, the rubber doesn't fit in the old metal so I have to unscrew all the old metal -- and it's not really screws holding it up, it's whatever you use when you use a wrench, so it takes forever with a pair of pliers (which is the only tool I really understand other than a hammer) then comes the drilling in the new aluminum and the sweating and the cursing and finally the darkness with the job as yet unfinished.
Why?