Save ”yes” for what you excites you, interests you, or is at the very least within your capacity. Not every “yes” needs to be enthusiastic but it should be authentic.
Some people have no trouble telling others “no” but it’s taken me a lot of practice. I’ve had to realize that my friends and family love me and value our relationship beyond any single request. Love isn’t transactional like this — or it shouldn’t be, at least.
Anyone you can’t say ”no” to is a walking red flag.