How do you keep the habit of exercising if your day is loaded with early tasks and you’re already exhausted at night?

I try to do some activity every day bit when I'm tired I'm atleast stretching. However you should always listen to your body.

You can always shift your sleeping schedule. If you're exhausted at night go to sleep instead of watching Netflix and wake up earlier. If something doesn't fit in to your routine it might be better to switch up your routine a little than stuffing exercising in a place it doesn't fit.