Do people go into content they don't know very well as a healer? Or is that frowned on?

I've always put off leveling a healer because I'm scared of going into fights where I don't have the mechanics memorized. I'm worried that I'll die to mechanics I don't understand yet and then everyone will be mad at me, because if the healer dies everyone else dies a lot of the time assuming there isn't another healer. :v I don't have the same fear tanking since they're so beefy that they can survive most mistakes and recover. But healers are pretty squishy aren't they?