Sure, every so often a lie in is nice, but actually doing it regularly (which is all too easy in the current climate) can be bad for your mental health.
Keeping a routine is important. What time would you normally wake up if you had school or work today? Set an alarm and still live a productive and full day, regardless of whether or not you can leave the house. Go to bed at a sensible time rather than staying up late because you have nothing to do the next day and you’ll see the benefits.
For me, my alarm is going off at 6:15 every morning. For most people this is excessively early but is needed because I start work at 6:45 and need to shower and everything first. But why not try setting an alarm for 8:00? You could still stay up until 11/12 and have a full night sleep, but your body will appreciate your routine. Then get up, make your bed and draw your curtains, have some breakfast and you’re set up for a positive and productive day!