Stall for time
When someone asks you for a favor, say you'll need some time to consider it. Saying "yes" immediately away might make you feel obligated and overcommitted, but taking your time to evaluate a request can allow you to decide if it's something you truly want to undertake.
Before you make a decision, consider these questions: How long will this take?; Is this something I really want to do? Do I have enough time to do it?; If I answer "yes," how stressed will I be? According to studies, even a brief pause before making a decision increases decision-making accuracy. You'll be able to more correctly assess if it's something you want by giving yourself a minute.
