There are people who feel reluctant to say 'no' to people. Even if they don't really want to do something because they are asked by someone they know they (family member, friend, relative) they can't reject. This later can become a problem when one is distracted by too many requests... It is a little bit different at work. This is the place when you are expected to contribute to the overall success. Because some employees want to demonstrate their commitment and desire to help the company they take on new responsibilities in response to the request of colleagues or management team. However, sometimes it is a good thing to say 'no' sometimes even to the management team.
Considering Your Options
First of all, you should understand that saying 'no' is okay. You are not a robot so you cannot take on new requests all the time. The common stereotype is that when you reject requests at work you are jeopardizing your job. You certainly can put your career at risk but not always. So the first thing you have to do before saying either 'yes' or 'no' is to understand the benefits and downsides. Not just for yourself, but for the company as well. So it is really important to recognize who are the real players behind the request.
If stakeholders are involved somewhere along the line and what you will do can potentially have a big impact on revenue enhancement you are better off taking this chance and agree to help. However, if the request has a low priority and you've got enough on your plate already it might be better to say 'no'. Although start with something like 'I would love to do it, but...' We recommend that whenever you feel like denying the request don't fire it out right away. Even if you know that's what your answer is going to be anyway. It is way better (for your reputation and relationships) if you try and understand the requirements first. Despite that, you have a bunch of assignments to complete within a very tight deadline take time and ask several questions about what you have been asked to do. Even without saying a direct 'no' you could explain how that would conflict with the commitments you have. Or maybe by starting to ask questions you will actually find this request an opportunity and agree to help.
Anyway, it is always better to learn more because you will be in a better position to make the right decision. Whether at work or at home you should always remember that by saying 'yes' to everybody and anytime you will reach burnout sooner or later. So considering your options is a must before making any decisions. Your career may be at stake as well as your life. We are not talking about saying 'yes' or 'no' in a particular situation but rather about the approach you choose when rejecting requests or giving your consent to help. By the way, this is an important part of a career management strategy. So you better take this seriously how you deal with requests that give you extra work.