Having dry hair is the easiest way to cause breakage. Think of it as your skin. When your skin is dry it's easier for it to crack and get small cuts at the slightest bit of friction. The same goes for your hair. Combing dry hair can cause unnecessary breakage and tangles.
Other than maintaining a healthy scalp that promotes hair growth and a well balanced diet, keeping the hair you already have is also very important. When your hair continues to grow from the scalp but breaks off on the ends it can appear as though your hair isn't growing. If the breakage occurs at a higher rate than grows, you lose noticeable length.
How to Combat Breakage
Keep hair moisturized (Even in protective styles)
Avoid combing hair while it's dry (Spray with water and apply leave-in or moisturizer first)
Sleep/ Lounge in satin bonnets (rubbing hair against dry surfaces causes dryness and breakage)