What makes it hard

Most people are not afraid of the word. They are afraid of the two seconds after it, and they fill those two seconds with explanation. The explanation is where it goes wrong: every reason offered is an invitation to solve the reason, and a request that has been argued down twice is much harder to decline the third time.

The second difficulty is that saying no to a request feels like saying no to a person. It is worth separating those out loud, because the separation is usually true and is almost never stated — you can decline the thing and be plainly glad they asked, and both halves can be said in the same sentence.