@Edneia0 Just stick to your cancellation policy- if the guest wants to cancel, that's up to them. There's no reason for you to take a loss because a guest had a change of plans or changes their mind. They have tied up your calendar so you can't rebook the date.
If you get a message saying the guest wants to cancel, do not accept, decline it. If you accept, that is counted as a host cancellation and you will get all kinds of penalties. The guest needs to cancel on their own, which doesn't require any acceptance from you.