What you think will happen if you choose what you want? 

It sounds too selfish, doesn't it: choose what you want? But the fact is if you devote yourself to an occupation that you enjoy you will be ready to sacrifice some worldly pleasures to succeed in it. When you are working very hard to master new skills, this is like play if you are enjoying what you are doing. This doesn't have to be something like a concert pianist practicing for 9 hours a day. Engineers derive great pleasure from seeing machine components running smoothly or working effectively because of their efforts.

Even cleaners feel joy from turning a dirty floor or surface to a clean one. So choose what you like is more likely to have good outcomes: a job well done, a career thriving, then deciding what you don't like but what you think you should do, or what others have set you to. In times gone by there was no choice. Now there is every choice, so capitalize upon it.