Asked in a different way: Can I still protect myself while taking an action that requires some focus on what I am doing? (i.e. it is probably not limited to stabilizing someone)
So the scenario would be:
- Two players are fighting one foe
- One of the players reaches 0 hp
- Second player wants to take one action to stabilize his friend because he has more than enough hp to survive one hit
The player does not disengage since there is no other backup.