Invest in your force multipliers

Tim Ferriss defines a 'force multiplier' as any 'high leverage' activity that substantially increases your effectiveness.

A good nights sleep (all 8 hours of it) is an obvious one. 

So is eating a nutritionally-dense diet. 

Exercise seems to work for most people (often giving them more energy to do more things), and meditation appears to give many people the capacity to tackle emotionally difficult problems (or just enjoy themselves more). 

Finally, I'd add a consistent writing habit to the list...be it a daily journal or a blog like this one. Something that forces you to crystalize and clarify your thinking, while polishing up your ability to communicate those thoughts to your peers.  

The point is, force multipliers are habits that dramatically amplify your performance and output. If you have to choose a habit to follow through today (and everyday), it's pays (literally) to first invest in one or all of yours.