There's a wide-spread notion that to achieve significant results one needs to work hard.
I have a problem with this hard work principle. Hard work, fruitful as it may be in the short run, will surely wear you out in the long run. Sooner than you imagine you will find yourself lacking any motivation and even ability to sustain quality output.
Don't work hard!!! You can work intensively, put in long hours, if your circumstances demand (and allow) that, but avoid as much as you can doing things that feel hard, exhausting, or in any other way negative. The work that you do should bring joy and inspiration - that's the only way to achieve your maximum, to become a great professional, to make record sales, to get promotion(and enjoy it).
All this doesn't of course mean that if you had a tough day at work you should resign the day after. Just be aware of the things that distress you in your job and make your best to minimize them. But, if you find that the hardships are inherent to the specific job and they outweigh the satisfaction it gives(if any) - maybe it's time to make a change. Maybe it's time to stop suffering and go find that job which will let you flourish.
Good luck!