Unless it's an emergency or call from your direct line manager or CEO, avoid taking calls when you knock off from work.

The work will still be there tomorrow. Keep your work and personal life separate. Your mental and emotional health is important. You owe this to yourself.

Avoid hitting the wall and burning out too soon. Metaphorically speaking, be a long distance runner, not a sprinter.

You are an asset and resource to your company, so they need you to be fit for the fight.

By standing your ground, you also gain respect. Take it with a grain of salt when dealing with the office grumblers who don't understand the words "no" or "not right now" - remember, it's just noise as long as management is happy with your work.