In order to be able to get this achievement you need to get hurt first. Getting shot is not something that will go by unnoticed. If you are not playing on hardcore then you can see your status meter in the lower right hand corner change colours to yellow, orange or red in the area you were hit.
Now all you have to do is hold
. I suggest you get into cover first. Hold it until the spinner completes a full cycle to stop the bleeding and then wait for the second cycle to go through for you to heal the damage.
Review 25 September 2014: Added button icons.