It is often seen as a weakness if you find it hard to say no to
someone. If you cannot refuse any requests from your colleagues or
boss, even when you already feel snowed under, that leads to
increasing stress. Either you will be discontent with your colleagues
who you believe to be inconsiderate, or you may be discontent with
yourself because you aren't able to stand up to your needs, not daring
anything.
At some point it becomes humanly impossible to fulfil all tasks and
demands. Colleagues and superiors do not know the reason for the
decreasing quality of your work, judge it as bad performance and in
the worst case attribute your failures to "unreliability" or
"incompetence". Your boss is hardly going to blame himself. In this
way diligence and good will can lead to failure and bad evaluations in
spite of the best competence. Your good nature is turning into a
problem.
However: Basically saying no cannot be a problem. If you are just
aware of what you are saying no to. Be aware that you never only take
a decision to do a certain thing or not. Because whenever you decide
to work on one task, you cannot work on something else at the same
time. Therefore every yes to one task automatically means no to
another, and often a yes to one colleague means no to another. You can
only then estimate the consequences of a decision if you have a good
overview of your commitments and plans.
When all tasks are written down, it is much easier to see which yes on
one side leads to which no on another. Then it is also easier to
refuse a colleague's request with a good conscience and self
confidence. If someone respects you as a person he will also respect
your decisions. Of course he will be disappointed whenever you refuse
a request. But: How much more is he going to be disappointed if you
say yes at first, but then don't keep your promise? Only one thing
builds up respect: that one can count on your word, be it yes or no.
To refuse assignments from a superior is less simple, or not even
possible you think? Maybe, but it doesn't matter. Your boss does of
course have a clear strategy, doesn't he. He has the overview and
knows the priorities. Therefore he can decide reasonably well what
needs to get done. Therefore you leave the decision to him or her:
Whenever he or she comes with a new assignment, then tell him or her
what assignments you already have and what is going to be delayed or
cannot be done at all if you accept the new assignment. Saying
something on the lines of "Oh, I've already so much on my hands ..." is
easily dismissed as whining. Everybody says that.
If you can clearly show what the situation is - without teardrops in
your voice - then your boss will first of all see how well organized
you are, and he does not see a general reluctance. Secondly, the power
remains with him - the power to drop the new assignment or to relieve
you from an older one. What you achieve with this strategy is to
empower your boss to a mutual advantage. Such behaviour creates trust
and improves teamwork. Very soon you gain more freedom and you can
perform better - for your boss and eventually also for your own career.