HazelGirl, I've posted this before, but I just wanted to share it with you., an email to my therapist and her response when I was in the same position as you, accepting her good graces.
Me: Also, last Monday, I came in for an extra session, but it lasted two hours. I only payed you for one hour, so I still owe you for an hour (maybe that's where the Freudian slip came in). Hopefully on Friday, I will receive support money and I will pay for four sessions, and be caught up. I am sorry that it is sometimes difficult to not owe you money sometimes. Starting in July I am only going to be able to come once a week and Kiddo once a week. It has nothing to do with therapeutic issues. I would love to keep comings as I have, but my resources have run dry and I just can't ask my folks right now. I am afraid of loosing more of myself to them.
Therapist: As for the issue of resources. I am not concerned about you owing me for sessions. I make my living, support myself and my child, by this work. I also do this work because I get personal satisfaction from it. I try to balance the two - so I offer a sliding scale, and I sometimes offer credit. I make these decisions on a case by case basis. When I have clients like yourself, who work hard, desire to get better, keep going when it is difficult and painful - I can happily settle for getting the bulk of payment for services from personal satisfaction. We can try once a week and see how it works. If it seems to impede therapeutic progress, then we'll discuss it and work out something that is mutually agreeable. We can find a way to make it work. I'm not going anywhere.
And now I will bow out. Best wishes to you.

She later told me I wasn't suppose to pay for the extra time. She does that on her own when she feels a client can benefit with the longer session, and she has the time.
ETA: Her reduced fee is as low as $0.00