Are you breathing correctly? It may seem like a silly question especially because we do it all the time. This does not necessarily mean we do it correctly. So let's look at it - when you breathe, is your upper chest moving only? To check this, feel your abdomen for movements when you breathe in and out. Try exhaling with a 'huh' at the end. This should result in abdominal movement's inwards.

Don't talk when the air has run out. A lot of people have this habit and don't realize it harmful. To get the feel, try doing it. You'll see your voice becoming increasingly croaky. So watch out for this and monitor yourself.

I myself have experienced a croaky voice the morning after a particularly demanding performance. I find gargling with warm salty water and a few hours rest to the voice helps. A lot of singers practice this.

VOICE FEELING TIRED
Yawning again will help with easing the tension in the throat.

Don't shout or sing for a while. Let your throat rest a little and recover. Whilst it is recouping, watch other things like your posture and breathing. 

Drink fluids. Have warm drinks and keep your throat lubricated. Swallowing will also help loosen tense muscles.
Have a good stretch - this will help loosen you up.