OK well, I kept this up for months. I am still doing it but every other day now, not each day. I will try to step this up. I think 5mins a day is a small investment to feel better. I am quite sure it did help, it pushes me to fix on being more positive and whilst I don't think I was really over negative, anything that steers us into more constructive ways of behaving is good.
So long story short ? I think it did work/help.