On example of negativity is underestimating yourself. You may think that you don't have the ability to complete your task, or you may feel that you have only little time.
If this happens to you, remind yourself of your competence and skill on a regular basis.
Complaining is also another form of negativity that can reduce your productivity. Whatever complaints you have, they will affect the quality of your work. Complaining will only make you tired, and it will reduce your ability to focus on completing your tasks.
If this happens, resist the urge to complain whenever you feel that you'll start complaining. This means that you will be taking steps to keep negativity out of your work life. Instead of becoming tired and bad-tempered from complaining, your energy level will be at its best.
Aside from underestimating yourself and complaining, worrying can also kill your productivity. Remember, worrying will not help you accomplish anything. If you think that the problem can be solved, then solve it immediately and don't let yourself worry so it won't waste your time. If it cannot be dealt with immediately, try to put the worry out of your mind while you are working.
If you still have the habit of worrying, remember what George Herbert says: A hundred load of worry will not pay an ounce of debt.
Finally, if you find that your negativity is severe, ask for some outside help. The more able you are to resist negativity on a regular basis, the more you will accomplish.