Until you’ve got your schedule filled, say Yes to as many things as you can. Even with a full schedule, you should often reconsider removing a standard item from your schedule and make room for a new Yes. Try out new things, whether that is a friendship, a gig or joining a cooking club. As long as it doesn’t clash with your principles and is reversible, you’re good to go. Most things have a trial period and don’t require lifetime commitment, so a Yes to a trial shouldn’t be too costly.
Become comfortable being uncomfortable. Even though you haven’t done something before and are objectively uncomfortable, feel OK with that situation and know that feeling comfortable will make the objective discomfort go away quicker.