Wow, I'm so lucky

Well, it's not like there are people who don't exist, so it isn't really something you don't take as normal

I'm referring to the fact that many people joke online about how they ''hate being alive"

Probably all the different combinations of sperm cells and egg cells that could have occured during conception

Have a look at this Harvard blog. You'll either find it quite interesting or incredibly boring. Basically it says the odds of you existing at all are pretty much zero.
http://blogs.harvard.edu/abinazir/2011/06/15/what-are-chances-you-would-be-born/

The chances of YOU specifically being born are slim, but the chances of SOMEONE being born are pretty damn good.