Before depression, I found it easy to be optimistic. Life felt good, or if it didn't feel good, I had reason to expect it soon would. If A = happy day and B = sad day, my life before depression was like this-
A A A A B A A A A A A B B A A A
Evidence favored optimism.
Depressed, I have become pessimistic. For the last year or so, life has followed an inversion of the pattern above-
B B B B A B- B B B B A B- B B B
Reent experience has taught me to expect sadness. If I am happy, I expect the happy feeling will soon fade.
Putting several "A" days together is very helpful in revising my expectations. If a good day does not necessarily lead to renewed misery, then I feel like there's a basis for hopefulness.