A full plate does not become larger because another good opportunity arrives.

Quality does not create room. An excellent opportunity arriving into a full life still has to displace something. The goodness of the offer is often used as a reason to skip that step. That is how people end up carrying more than they can hold while every individual item was justified.

When something excellent appears, ask what comes off the plate. If nothing can, the honest answer is no, however good the thing is.