When I came back to judo at the age of 51, the wise "elders" of the old Judo Forum told me to take it easy, be careful, and watch out for injury. Two months in, I broke my tibia plateau, tore my ACL and spent six months in a leg immobilizer. After recovery and physical therapy, I finally got to get back on the mat. I've seen other guys with similar stories over the years.
It was a smart thing to take time off from practice, but still keep attending practice. You can learn a lot from watching, but most of all, attending keeps your heart and mind in judo. While I was recovering, I didn't miss a practice. I sat on the side of the mat and studied my vocabulary and technique names. My sensei sent me kids to quiz on terminology and kept me engaged with the other club members.
When I wasn't on the mat, I hobbled around the weight room on crutches and worked out everything I could except the bum leg. I wanted to keep my conditioning up, although it was tough to keep cardio strong. When I finally was cleared to come back by my doctor, the judo came back quickly.
That was several years ago. I eventually earned Nidan rank and I have my own club now. Whenever I get older students, I urge them to take it slow. I've been fortunate that we haven't had any serious injuries at practice. We've had more guys get injured playing soccer or baseball at school. When they had injuries, I encouraged them to keep coming to practice. That keeps them in the club and they usually come back to judo when they heal.
I'm 56 now and still doing judo. I just have to remember that I'm not 16 and I do fine. I get inspired by guys who are 70 and 80 who are still going.