One of the major emotional problems of the world is perfectionism. So many people are excessively worried and stressed about their own weaknesses. According to the psychological book I've been reading (Feeling Good: The New Mood Therapy by Dr. David D. Burns, one of the leading psychologists in cognitive psychology, which is my favorite school of psychological thought), perfectionism is mostly caused by two types of illogical thoughts: all-or-nothing thinking and should statements.
One day, on my mission, I was having a really rough day. I felt angry at myself for not being perfect in certain areas, angry at the Lord for not making me perfect, and generally frustrated and discouraged. With a prayer in my heart for help, I pulled out the most recent General Conference Ensign. There I read Elder Oaks' talk, "Good, Better, Best" (Ensign, Nov 2007, 104–8). As I read, I suddenly realized that goodness is not an all-or-nothing thing. It comes by degrees! I wasn't a perfect missionary, but I was a good missionary, and I was sincerely striving to be better. Perfection does not--indeed, it cannot--come all at once. Sometimes we think that we are either perfect or the scum of the earth. Obviously, there's a lot of room for growth in between.
We use the word "should" all the time. We all have our own ideas about how the world "should" be. However, it is helpful to think carefully about exactly what we mean. One strategy is to use the word "if." For example, if I just say, "I should be doing better than this," I feel guilty, discouraged, and angry at myself. On the other hand, if I say, "if I work a little harder to serve, then I will be happier and have the Spirit more," then I will likely feel encouraged and want to try. It works the same way when you use the word on others--when you think, "He shouldn't have cut in front of me," you usually feel angry. So instead, think, "It would be nice if he hadn't cut in front of me." I've found by experience that talking back to your own illogical thoughts can be very helpful.
The credit for these ideas goes to Dr. David Burns from his book, and, more importantly, the credit belongs to that God who helped me understand these ideas and whose Spirit of truth taught them to Dr. Burns in the first place.