I'm dealing with Plantar Fasciitis and a minor tendon tear in my achilles tendon. The achillees is not as painful as the plantar.
Over-use injuries like plantar fasciitis, shin splits (to which I used to be very prone), and IT band tendinitis are often caused by dysfunctional movement habits used repeatedly over long periods of time. Movement dysfunction propagates through your body, as the muscles in one area are affected by the function of muscles in adjoining regions. Over time, this cause micro-trauma to accumulate until it crosses an injury or pain threshold.
Unfortunately, the cause of the pain may be remote from the region that hurts, and there may be multiple inter-related issues, so alleviating the symptom (i.e. pain) may not remove the cause. Tight muscles can play a role in this problem, too. For example, consider a scenario where someone's plantar fascia is painful because it is continually over-stressed because their feet severely over-pronate, because their calves are habitually tight, so they have lost dorsiflexion in their ankles. Massaging your feet and stretching your calves may alleviate pain in this case, but you may not have addressed the problem. You calves may be tight because your hips are dysfunctional, and so you and your body have learned to compensate by off-loading the proper roles of the hips to nearby muscle groups that become chronically over-stressed or under-stressed (e.g. lower back or legs). The real solution in this case is to address pain, tightness, and inflamation as it occurs, but also remove the cause of those issues by retraining the hips to provide proper function during your movement. Even that solution may have multiple factors, as there may be a combination of joint mobility, motor control stability, and muscular strength issues all mixed together.
Restoring joint mobility, motor control, and strength with rehab may then allow to to attack an even deeper cause--dysfunctional movement patterns, because your movement can be dysfunctional and injurious even when all of the component muscles and joints have the proper range of motion, muscle length, and strength when tested individually. (This is like identifying a software problem, after all the hardware checks out).
I strongly recommend having your movement assessed by a Physical Therapist (MPT or DPT) who is qualified to perform a Selective Functional Movement Assessment (SFMA). (See functionalmovement.com). The PT should quickly be able to drill down to the most dysfunctional components of your movement, and give you guidance on how to prioritize and tackle the issues he finds, as well as explain how that dysfunction may relate to the pain you experience, even though the underlying problem areas may be pain-free.
(I used to believe that my arches were falling, I had bad knees and a weak ankle, and that eventually I would have to give up long-distance hiking and start wearing custom orthotics, but in the last two years those issues have been almost entirely resolved to a degree I would not have imagined possible, because I started looking for the causes of my injuries in my movement, as opposed to continually chasing symptoms of pain and tightness.)