What are the hardest and most useful skills to learn?

"Doing it now" I feel doing things now is one of tough skills to learn.

We generally makes plan and postpone it for next hour, next day or next month whether it is studying, learning new things or anything else.

If we see our past, whichever things we have completed on that time effect our present right now.

When I was in 12th grade , I thought , in Engineering I'll learn bike driving In Engineering , I postponed it for when I get a job. When I got a job, then after switching the job. The day never came.

Now I learned it ( 2 years back ) Benefit : I can go anywhere by myself. (otherwise I have to arrange for bike and then a friend as driver to go anywhere :) ).

The above is just one example, I am sure there are many others.