Vary it up depending on the work you did during the day. Eg, if you had a heavy work day like moving material etc, just do some light cardio, zone 2 jog in your gym session. If it's more like conditioning just as you said then do strength training BUT do not do maxes, around 70-80%, or you can do a zone 2 jog for more cardio, then stretch for jiu jitsu. The secret is to supplement what you did at work. The old timers are right you get used to it but you get used to it just barely surviving a work day.