We have throughout our lives been taught to not praise ourselves. It is considered bragging, putting on airs, or just plain in bad taste. We can even remember sermons about it like "Pride goeth before destruction, and a haughty spirit before a fall."
Why is it considered bad?
Perhaps because in a lot of cases it is used to elevate one person over another as if in some way it is proof of their feeling of superiority. When used this way we would probably agree that it has a negative connotation and we would consider it in poor taste or a destructive statement.
Can we argue that when we do something good and praiseworthy that we can at least acknowledge to ourselves. Not in a vain way but as a recognition that we do good things as well as they bad things which we are so quick to point out to ourselves.
When we only recognize the things we do wrong we are out of balance and lose our perspective. If we only focus on the negative then we are not being fair to ourselves. After all we we see others as a mix of good and bad actions and accept them when the good outweighs the bad.
Can we do no less for ourselves.