Kevin Kelly says the right balance is to spend 1/3 of your time exploring and 2/3 optimizing. 

Exploring means looking for new projects, pursuing new skills, and taking new paths.

Optimizing is about honing your current skills, maximizing the return on your efforts and pursuing mastery.

We spend the early part of our career in exploration mode and then we tend to stick to optimization. It’s harder to keep exploring new options as we advance because we’re incentivized to optimize.

Exploring new projects & pathways keeps us in tune and interested. Optimization without exploration most likely leads to stagnation. That’s too much rhyming for one sentence, but it makes the point.