Nothing Last forever!

I am having stuffs surrounded by me and using all in my daily life seems automatic to me. I don't know exact use of automatic because this term automatic is new to me, I am talking about our brain, our nervous system or Automated nervous system we call it in terms of science but for me its automatic.
Doing every day every thing and using pretty much basic tools of life and though some tough trails I think I learn them how to use it but still I didn't get them at all by heart.
People say if you do a task continuously 21 day then that task going to become your habit but I tried and it didn't worked. I don't know may be I did it wrong or my be I don't want that task to do at all. I think that the answer I don't want to that in first place and some how I just able to manage to do it in 21 continuously day that is just waste of time and a damn good lesson.
I don't know why I have to make a mistake and learn the truth about life why can't somebody clear tell us in warring that if you don't want to do it in first place you will wasting your time, but they have just say give it a try and find out yourself.

"Mistake are easy to Make  

and 

not easy to Undo, 

but Lessons are tough to remember 

but 

easy to Learn."