I start playing through some of the chords again to give myself a break between verses: sometimes repeat the last line or play around with the chords to find a sequence I like. If you're in a band and somebody else is playing a melody instrument, whistle, fiddle, lead guitar etc. you can get them to do a repeat of the last line to give yourself a rest. I also (horror of horrors) put extra bars in now and again to let myself catch a breath between lines. I figure as long as you keep the beat regular it doesn't matter and if you're doing it with a group practice where you're going to put them and then be consistent with your changes. When you're playing dance music you need to stick with a form but when you're singing you're allowed to be freer and more expressive as the mood dictates. Don't let the drummer or the guitar player boss the singer around.