Take the time to step back and define your position
A reflex: to want to respond immediately and, therefore, without prior reflection.
More effective:
. Give yourself time, even of short duration, to process the
request: How does it strike you? Does it surprise you? If so, how? What
does it reveal? What information does it offer about the
co-worker's perceptions and expectations?
. Make sure that you understand the request and that you have all the information you need in order to take a position.
A no pronounced too quickly may cast doubt upon its validity.
Express briefly your position
Fight against the tendency towards endless justification. You
only need to formulate, in a few words, what you are saying no to and
why.
There is generally a valid reason for refusal: this reason is to be expressed clearly and concisely.
It is not by elaborating and repeating yourself that you will get your co-worker to acquiesce.
Accept your co-worker's displeasure
It's impossible to always make everyone happy!
Managing means sometimes displeasing or upsetting people because
it involves reconciling individual and collective interests,
arbitrating along the lines of fairness.
However, it is better to intervene if discontent sets in and
weakens the relationship. In that case you can, with cool heads, discuss
the refusal, the way in which it was perceived, etc.