How much working out is too much?
I'm probably the master of overtraining. I did it for years.
Too much is, well, too much. It is impossible to make that determination for another person - until his/her symptoms become evident.
Back in the day (in the 60's and 70's), people who worked out did so for athletic reasons. The whole "fitness craze" thing had yet to begin. I was in my competitive heyday until the mid to late 70's.
I thought I could continue at a competitive level until my "epiphany" at about 45 years of age. Slow learner.
I worked out tired. I worked out hurt. I worked out despite everything my body told me. I was "retired" in 1980; but I didn't get the memo until 1997. For 17 years it wasn't fun; it was work.
Fitness is healthy. Trying to be something you're not is unhealthy. Listen to your body. If you are tired, back off. If you are hurt, do not continue. Program your rest. If you are not a competitive athlete and you are your own coach, study your activities and study you. Exercise physiology is a science. A fitness lifestyle is an art. If you want to make it a life-long habit, give yourself plenty of rest...and, above all, have fun!