If you feel tired rest, simple, no point in overdoing it if you feel you really need a break, i have taken a week off ( sometimes more with a flu etc. ) on several occasions and always come back feeling better, stronger and having a sharper focus than before the rest. That being said though 3x a week weights training only for an hour or so per session isnt a lot of strain on the body if you live a sedentary lifestyle, i work a physical job as do many others, rest is sometimes a requirement.