How do i tell my doctor im not going to do the exercises shes requested i do without being rude

To continue from the title I’ve seen her 2 or 3 times now and between the visits i have barely been doing them this is particularly because I’m very busy and particularly because i do just tend to forget but i also think the only thing that will come out of me doing them is knowing what i have but there are no conditions that match my symptoms that have a form of treatment so the way i see it is that no matter what i do I’m never going to get better so whats the point.

Please can someone give me a good way to convey this to my doctor without sounding rude or like I’m giving up on life or something like that.