There's no shame in testing your limits and trying to grow as a player.
That tank that sprints off and pulls wall-to-wall is probably learning too. You're both learning off of each other.
Playing How Low Can We Go is what makes healing fun. What can I get away with? How much DPS can I do?
I think every healer who wants to optimize their play does this to some degree.
Mistakes will happen. We have to let them go.
