Working in a correct way

Understand only the essential
First of all, Proceed your work with understanding will ultimately save your time.
But you don't need to know everything, just the essential, which can be 20% out of the whole knowledge. How to know whether the knowledge is essential? The testing stone is if you acquire or well-equip this knowledge, it could save your time in understanding most of the materials that you MIGHT NEED to understand; or it could help you to progress with the works that you MUST understand. The main purpose of acquiring certain knowledge is you could use it, if the knowledge just potentially useful, you should acquire it in your leisure time :)

Don't Procastinate, work solely on single important thing
Another thing is don't procrastinate.
Say the most optimize way of completing certain things where one can think of is A hrs. Thus you have to spent at least A to finish it. If you can finish it faster, the less stress you have, the more pleasure you have later. You have to allocate yourself some space of pleasure, but not spreading it throughout the working time which will in turn bringing yourself stress. Keep a time log on what you are doing which could help you to better manage your time. After a single day, thinking of what you are doing over a day, what could be improve on that, and so on.

Relax yourself while working
But remember, in order to let your creativity flows, you have to RELAX your mind and body when doing your work. With this, you not only can work longer, but also your mind will able to flow more perfectly and ultimately increase your effectiveness in doing certain things. Try to let go all the stress, relax yourself, control your breath(slow, and long breath), let your mind only thinking of your work, but NOT TO HARD. Thinking of meditation, one way of meditate is to concetrate and count your number of breath, after that, you will feel that the external world IS NOT RELEVANT to you, and you are having a joyful experience in couting your breath. Same think for concentrating yourself on your work. Not too hard, yet not too soft :)

Working as Leisure
If you can feel the hapiness in working, as you work in the way of meditation, what's the different between working and leisure? Working can be a leisure too~ If you are feeling stress, certainly you are in a wrong mindset. Stress won't let you go anyway, the only function is to push yourself work harder, but if you are stress, you becomes tired easily, and your mind is feel with stress you can't let yourself free flowly. If you treating working as meditation, you would concentrate on it till finish, yet won't have any feeling as stress.