Money Back Guarantee

I am a weight loss coach and I work 1:1 with clients right now. I have a lot of tools I give my clients to use so the A lines and then we spend most of our time together understanding their models around why they aren’t doing the A they want and what thoughts are getting in their way (i.e. showing them their minds and helping them see how to manage them). I know because of how successful I have been myself using what I teach that there is NO way they won’t get amazing results if they commit to working together for 6 months and do the homework we talk about each week. Now, I have clients that don’t do the work and we work on their thoughts so that they do. But I want to offer to my clients that if they aren’t satisfied after 6 months having all the sessions and doing the HW they will get their money back. But I don’t see anyone else doing this and my thought is….I shouldn’t do this because no one else is. And my other thought is I don’t know how to quantify if they are satisfied. I just love the guarantee in scholars and other programs I have done and for me it partially motivated me to do the work in the first few weeks or month and then it was so obvious there was tremendous value which is how I feel about my program. So my problem is I am unsure if I should offer a guarantee and even if I did, I don’t know how to articulate it. Help! Thanks!