Any meditation or spiritual exercise you do should be done daily. Skipping a day will cause any progress you may have made to be lost. Overdoing a breathing exercise is when you push yourself despite feeling pain or discomfort. Pushing breathing exercises can overstimulate your nervous system and harm you. If the breathing exercises feel good or energizing, you are not overdoing them.
The 40 Day Meditation Program available in Library of Thoth is a good place to start with meditation. Some links in the 40 Day meditation Program PDF are broken. PDF copies of the information from the broken links are in Library of Thoth.
40 Day Meditation Program
Library of Thoth