A voice in my head telling me to do something that I already know I should do won't make the emotion go away, and, for me, the obstacle in these sorts of situations is definitely the emotion.

A voice in your head isn't a simulation of what the idealized person would do. What you want is for your simulation to be is the experience of observing that idealized person actually doing it. Otherwise, you are just thinking (system 2) instead of simulating (system 1).

To put it another way: a voice in your head is Far, a simulated experience is Near -- and Near has far more influence over your emotions (no pun intended).