Ah! So, you have to let Chompa tell the whole story, but you have to stop drinking early enough that you can remember it.
There's a little hint when it says "A tiny voice tells you to quit while you can." After that, you should Retire.
You then have to remember what you learned from the conversation to unlock the trophy. This is probably obvious. I don't think I can protect spoilers here but maybe if I say spoilersblahblahitsthemiddleoneblahblahspoilers you can work it out if you look closely and can ignore it if you prefer :D