It helps to understand sleep cycles and how to use two-sleeps (or three) and catnapping.
Sleep usually has a cycle where you go deeper and deeper into REM or dream sleep and then climb back up to near waking before dipping back down into REM. In most people this is a 90 minute cycle, but some may be a bit more or bit less. Sickness also tends to throw it all out of whack and require you to sleep more.
So how to handle it?
A) stay healthy, taking vitamins that you may be deficient in, i.e. extra D if you are indoors too much, Omega 3 if your muscles ache, C if you need to heal something even just a strained muscle.
B) plan two sleeps. When you start to feel drowsy after 5pm, immediately go to sleep in a dark room with a beanie like hat over your eyes and temples for extra dark. Have an alarm set for 90 minutes. Later on in the evening, set an alarm for 6 hours before going to sleep.
C) if you really can't sleep 6 hours because things are hopping, do another 90 mins or 3hrs sleep when you start getting groggy. Keep track of the debt so that you can catch up with the leftover later, even in the daytime in a closet somewhere.
D) Get control of your mind. Do meditation and relaxation exercises. Learn to catnap. When you have a chance, close your eyes, empty your mind of thoughts, relax, sink down into sleep. Even if it only lasts 2 or 5 minutes, it helps keep you going until you can do a full 90 min cycle. Learn to catnap sitting up in a regular chair. Practice good posture so your upper body muscles are strong enough to hold you even when your chin drops. Free lifting of weights helps.