Lost 45, Gained 20

So I lost 45 pounds on SO workshop, but also gained back 20. Wrong thoughts, followed by wrong emotions, and mostly wrong actions to overeat.
Since it took me a year to lose these 45 pounds and I did it carefully and consistently, I thought I got over this problem for life, but apparently the brain can always circle back to old ways.
Sitting today at home, 20 pounds overweight, I decided I could keep sitting and feel bad or try to coach myself to feel better, or I can actually go out for a walk in nature and feel better.
So I got up and found only one pair of leggings that would fit me (since I got rid of all the larger size pants I used to have) and for the entire walk I felt as if I was carrying a suitcase around my thighs and felt heavy, out of breath, and most kept hearing my brain beating me up for the damage I’ve done.
From this spot I found it very challenging to restart the protocol.

Would you suggest to me some mindful thoughts that are better than ‘I know I’ve screwed this up and I have to lose those 20 pounds again’?