A shame spiral characterizes the loss of self-control over something that makes one feel worthless and pathetic. Due to these feelings of low self-worth and guilt, the action that triggered the shame spiral is repeated and the degradation of one's self continues. It is a cycle that repeats itself, bringing one down further as it repeats. Example triggers for shame spirals could be excesses of junk food, alcohol, meaningless sex, buying unnecessary gifts for oneself and the like.
Out-of-shape Bob: "I had McDonalds for lunch today and now I am ordering myself a pizza. I am on a serious shame spiral. I hate myself. Ugh."
Shopalholic Sue: "My rent check yesterday bounced but today there was this cute pair of shoes on sale and I had to buy them. How do I get out of this shame spiral?"