What is one reason it is important to treat plantar fasciitis, letting it heal completely before more strain, especially for athletes?

After an initial period of acute inflammation, chronic inflammation sets in, accompanied by adhesions & fibrosing of the fascia. The plantar fascia thickens with chronic inflammation. With repeated stress a bone spur may develop on medial aspect of calcaneus. Healing is slow as poorly vascularised, so great care must be taken.