Have a friendly conversation about what has been happening lately when they make plans to do things with you, the cancelations. The waste of time on your part. Allow then to know you're beginning to question if their time with you is as important to them as it is you. Let them know yes life happens, however it's been three back to back cancelations and no excuse as to why just sorry I want be able to do tonight. We'll either have to set up plans days in advance to give room to move plans around if need be. That's only if the time together is important to you. With that being said should we evaluate our friendship maybe we're outgrowing each other and that's fine. At least we can back of and remain friends. I leave for you to decide since the cancelations are on your part. No shade intended, just being a real friend here. How would you address a friend that keeps canceling plans constantly?

This one is simple you speak with your friend with kindness. Speak how you feel that by them making or agreeing to plans y'all have and then they cancel constantly, which is an inconvenience to you because you have set aside the time and now it is a waste. Just honestly let them know they can not continue to take your time for granted.