Because doing something we don't want to do but HAVE TO do is one of the shittiest ways to live your life and we actively try our best to delay such things.
Mainly because its we will eventually be forced into that lifestyle just to stay alive.
However...
Once you find that REASON to persevere through that shitty lifestyle, ie. A Family, a loved one, obtaining materials or upgrading your living conditions...
Suddenly its not so shitty.
-What allows you to persevere?