Dubstepped I wrote what I wrote because when I was reading your post I thought 'did I write this??' You sound so much like me. I have a great, frightening memory too. It makes me be very conscientious of everything I do. I've lived my whole life trying to please everyone and be good. All the time. My mistakes in horrifying detail come to haunt me at night and I lay there saying to myself 'stupid! Stupid! Stupid!!' Lol. I wish I didn't have the memory I do! It would be so much easier to just forget. You said some things in your post that really resonated with me. I know how it feels to worry about what witnesses will see, and how anxious this can make you. The grocery cart thing is something I've learned very slowly, and it's subtle but powerful. To free my mind from the fears and replace that with the joy and confidence of freedom.
Regarding Syme's comments above, the more time that goes by that you're not an active witness, the less possibility that some issue needs to be 'handled.' Even if someone sees something and tells an elder, if you haven't been an active witness for years, they will probably ignore it. If you were trying to be an active witness that would be different.
I even go to another church, and I'm sure witnesses have recognized my distinctive car in the parking lot. I have to live my own life. Let them get all upset if they want to, but they have no more control over me than I let them. For me it was a gradual self realization.