Death is inevitable, but Life - that's the tricky bit where things happen.
What I think we fear is rapid, pronounced, and uncontrollable changes to ourselves, and because of this we have a form of personality inertia - something that resists rapid change.
It's good to follow the path of personal happiness to some extent. People tend to get upset however when you drive a steamroller down it.
Allowing yourself to smile takes 99% of the effort.