These are all great suggestions and I really second what everyone has said. I’d also like to just mention that you should practice your energy work a bit more. It’s actually one of the things that I feel we as witches and practitioners should constantly be practicing. It can help us with, as @Francisco said, release our excess energy but also make sure we’re not depleting ourselves. It is also very helpful in making sure that when you cast a spell, you’re not using all of your own energy.
Draw on the energies around you from the Earth, from the elements, from whatever you have. Raise energy by dance, music, or motion if you constantly feel tired or drained after casting a spell. Chances are you’re just depleting yourself. Afterwards, as others have mentioned, be sure to grab a light snack and something to drink. Rest if you need to (naps are great) but if not possible, just take it easy for a bit.