Playing Mercy a lot can be harmful for your health. When I'm getting targeted, I literally end up screaming "help me" at the screen right along with her (Mercy) as I frantically jump around trying to get a teammate in my line of sight. Too bad they are all off in 5 completely different directions. 

Then you'll have the one person ask for you to heal them as you are walking back to the objective because no-one protected you...

The worst is having just res'd your team and hearing "Justice rains from above", "It's high-noon", etc. It makes me want to cry, but I just die a painful death instead as my body (and wings) ragdoll against a wall. 

Edit: Every now and again I'll get a team that is determined to protect me, and that feels incredibly satisfying. 

P.S: "I'm not a miracle worker, well not always."