Reflection is a reverse image of something in a mirror. Self-reflection is a gentle investigation into the inner self so that we can understand ourselves and make changes if necessary. This is not self-criticism or self-justification. It is looking at ourselves with the cool eye of observation and a warm compassionate heart.
I like this photo which symbolically shows some of the complexities of self-reflection. The perfect reflection of buildings next to a canal has been disturbed by some swans. You have to look carefully to see what is going on. Then there are the hidden depths in the dark tunnel.