There are many times that singers should rest their voice for 24-48 hours. This means absolutely no talking. I have worked with singers who sang for 4-5 hours several nights in a row and the speaking voice range drops to a lower range and the singing voice cannot reach any of the upper range. This is a sign to go on voice rest. It may take a few weeks for your voice to be a hundred percent but it will slowly get there.
I recommend to singers who are actively singing on tour, at festivals, in club settings, in church, and in the recording studio to rest the voice one day a week. This renews your talent and helps ensure longevity in your career.
If you have been sick and have laryngitis you must immediately rest your voice several days in a row and consult a doctor to get proper medications to help heal the condition. A singer cannot tarry with getting proper care on the onset of being sick. Your singing obligations usually have to be met, so the key is taking care of your voice quickly.