It can be good to take a break from physical exercise sometimes. But if you feel like the break should be over, take a look at your diet. I'm sure you know this, but exercise causes your muscles to get a ton of tiny rips in them. This is why moderate to heavy exercise requires a protein boost, particularly in the hour after the work-out is over, which is when your muscles use the protein to rebuild and grow... Without the protein, they just stay ripped up. And then your body is stuck with injured parts to deal with, which can be exhausting, because it's forced to work to repair them, without the tools it needs to do the repairs.

The endorphins from the exercise should help you through the grief---but you won't get those endorphins if your body is getting depleted through the exercise instead of benefited. So, often, if someone is tired even though exercising regularly, it's a simple matter of making sure they get a good shot of protein after their work-outs, like via a protein drink or another similar form.