It’s not easy but sometimes we have to say no. Not just in life, but also at work. This can be difficult to do when asked by a superior or even an equal at your job but it will save you pain in the long run. I do believe there is a certain initial period where you should not refuse extra work or the particular work you’re being asked to do because you need to prove yourself and your worth to the company. This is generally six months to a year, depending on your industry, the length of time it takes to ramp up in the new job and the average length of tenure in your company. The only exclusion to this time rule would be if you’ve been asked to do something unethical or illegal; then I would strongly advise you to say no.
In a less serious situation and after that initial time period has passed – say you are being asked to take on a tenth client and it means you’ll have to work 80 hour weeks and you are not up for it – tell your boss. But don’t just say no; you need to come up with an alternate solution and present it to him or her. Maybe you know of a colleague whose background is a better match for the client or a colleague is interested in professional growth in the client’s focus area. Perhaps you could offer to take on the work and relinquish some other responsibilities.
Personally I found myself in a situation where I felt what I was being asked to do would damage my professional reputation among certain audiences. So I said no. One of my managers was surprised but respected that I felt comfortable saying no and that I was able to explain why I felt it was a bad decision for the organization and for me. I did not experience any negative consequences on the job afterward. If you find that you do, you may question the people with whom you work. There are people out there who will respect your priorities and integrity.