Self-respect is choosing not to participate in your own diminishment.

Diminishment often needs your cooperation. The joke at your expense that you help along, the description of yourself you repeat because someone else said it first, the role you keep playing because it is expected. Others may start it, but it usually cannot continue unless you agree to hold up your end. Withdrawing that cooperation is often quieter than a confrontation and does more.

Watch for the moment you are about to join in against yourself and simply do not. Let the joke sit unlaughed at, leave the self-deprecating line unsaid, decline to confirm the version of you being described. You are not making a scene. You are just no longer doing the work of making yourself smaller.