One of the most important skills a singer can possess, and one that only comes with experience, is the willingness to sing the wrong thing.  

When we start out, particularly if we are singing in a group, we are often terrified of getting it wrong and showing ourselves up.  This leads to the development of another skill, an undesirable one, which is following the next singer by staying a fraction of a second behind them.  We can get so good at doing this that we begin to believe that we are singing independently and not following anyone, until the person on whom we rely misses a rehearsal, and suddenly we don’t know what to sing!

I often tell singers that if they occasionally sing in the wrong place, or sing the wrong note, I take that as a very good sign.  It means that they are thinking for themselves and not relying on what they hear from their neighbour.  Of course, we want to get it right in a performance - no mavericks there please - but rehearsals are for practice, and I believe we can only really practise if we are willing get it wrong.

The singer who follows another singer will be fine most of the time, as long as they are standing next to a confident neighbour who knows the part.  But that singer won’t develop their music-reading skills, and will never be able to sing at sight.

So I encourage you to throw caution to the wind when you rehearse.  Only by being willing to get it wrong will you truly get it right.