Busy is the polite word for a choice you already made. There is usually time, and it went to something you wanted more, which is allowed. The problem starts when you use the word on yourself, because then you stop seeing the choice and start believing your schedule is happening to you.

Try swapping the word in your own head for one day. Instead of too busy to call her back, it was not a priority today. Some of those will sit fine, and the ones that sting are telling you where to move something.