For some reason, most human brains retain negative memories far better than positive ones. Especially when we are not feeling good about ourselves, our lives, our love relationships, we often forget to notice what is going well. In fact, we need an assignment to look for small good things in life. This is not about "positive thinking" but rather about being present, aware, and mindful of what is happening in your immediate world, taking in the positives if you are already seeing the negatives. It can become an important part of mental hygiene.
Buy a small notebook--one that will fit in a pocket or a purse. Each day for the next two weeks, use one page to record 3 things that happened during the day that were good, gave you a smile, or allowed you to see beyond the gray. These can be tiny tiny things in your world--a squirrel running up a tree, making scritching noises with its toenails, a mushroom growing in your yard, the texture of the lettuce in your salad, hearing a favorite song on the radio....even, if you can't find something else, having a bowel movement (because not having one can cause more issues <g>). If you have kids that are constantly picking at each other, try to catch them at a moment when they are playing quietly together. Watch your partner, look for something he or she is doing that is kind, good, caring...even if they do it everyday. Take a moment to appreciate that meal, the made bed, their warm (or cool) feet. Even better, express your gratitude for the little positive somethings they bring into your life (even if you are often angry about what is missing.)
At the end of two weeks, read back through your journal and see if there is anything to learn from your writings.
This exercise is also one that families or couples can do. At a family dinner, have everyone at the table say three things that were good about the day. Or when you go to bed, trade gratitudes with your partner. Blog them, put them on Facebook if it feels comfortable, share them with a friend.