A preference is easier to honor when you stop disguising it as an excuse.

Dressing a want up as a constraint feels safer and works badly. Saying you cannot make it, when the truth is you would rather not, invites people to solve the obstacle you invented, and now you are managing a fiction on top of the original wish. It also teaches you to treat your own preferences as insufficient reasons. Most people accept a plain I would rather not far more easily than they accept a schedule they can rearrange.

Try stating one preference this week without a supporting excuse. Say what you would like, not what prevents you. If the honest version feels too blunt, add warmth rather than justification.