Updated: May 28, 2020
You need to train intelligently, not hard. Tennis is a physical sport. If you do not listen to your body, you will get injured. What does this mean? Well, if your lower back is sore do not play until you feel better. If you feel energized, great, do a hitting session and some weights then take the next day off so your body can recover. On off-days walk, move, crawl, play another sport, do some stretching.
Incorporating visualization during your off-days would give you a monstrous advantage. Science is coming out with studies that your body does not the difference between an imagined experience and an actual experience. Thus, you can literally have an “actual training session” without having its physical demands. Be the master. Intelligently organize your training based on your intuition.