I don't think you should just do what makes you happy. Do what makes you great.
I think people are surprised when I string two sentences together. But I had a fiercely academic upbringing.
Never trust a man whom you know to have acted like a scoundrel to others, whatever friendliness he may profess to feel towards yourself, however plausible he may be, or however kindly he may behave; be sure that, the moment he has anything to gain by so doing, he will "throw you over."
Thinking of Plan B muddies up your chances of succeeding at Plan A.
You do not have to be fearless, just don't let fear stop you.
I don't think you should just do what makes you happy. Do what makes you great. Do what's uncomfortable and scary and hard but pays off in the long run... Let yourself fail... And pick yourself up and fail again. Without that struggle, what is your success anyway?