Saying No

I do a lot of work for free and then have paid programs and coaching etc. There are people in my classes that I love but always ask for more of my time and energy. For instance, one of my students can’t make our upcoming group coaching call and has asked for a one-on-one call with me. My one-on-one sessions are more than the cost of the entire course but I struggle with how to say “no” because I want to go above and beyond and be generous with people. How should I navigate being “generous” and not open the door for people to ask for far more than what I have offered in my course outline or to simply say no professionally.