When you rehearse saying no

You cannot attend the event. Your message now includes your schedule, your energy level and evidence that you care about the host. Every sentence seems to need another sentence protecting it.

They need to know whether you are coming. They may appreciate warmth and timely notice. They probably do not need the complete argument you have been having with yourself.

“Thank you for inviting me. I cannot make it this time, but I hope you have a lovely evening.” If this is a close relationship, add something personal that you mean.

You cannot choose every feeling your answer creates. If there is a practical consequence, discuss it. You do not need to keep enlarging the explanation just to eliminate the possibility of disappointment.

Read it once for clarity and kindness. Then send it when appropriate. The aim is an honest answer, not a sentence powerful enough to control the entire conversation afterward.