2 days ago was my 6 month anniversary.

Today is the 6 month anniversary of the day that I accepted my PhD advisor's offer to join his lab after more than half a year of intense stress and uncertainty and anxiety and disappointment with the process of finding a lab to join. It was the first time in my life I started getting constant physical anxiety symptoms. I was suicidal and ending up drunk in the ER getting stitches for self harm every month or two.
At the point that he made the offer, he was my last hope. Due to a lot of options falling through and my fairly small subfield of interest, if he hadn't made the offer I would have had to leave my PhD program (and then probably not stuck around in the world for much longer)

He took a chance on me to keep me in the program. By offering me a position in his lab he was agreeing to take financial and academic responsibility to me for at least the next 5 years. I hadn't been rotating in his lab long enough for him to really gauge my competence and skill. He was giving me a chance and taking a risk based on faith so that I could stay in the program.

My advisor has more than 30 years clean and sober... he actually got kicked out of his first PhD program for his drug use before getting clean, and now he's a tenured full professor at a prestigious university and an established and respected member of his field.
He does NA. I do SMART Recovery. I had a conversation with him about my mental health when I had 3 weeks sober and mentioned that I didn't drink. He asked how long I had and I was embarrassed to say about 3 weeks. He was supportive and has asked me about it a few times since without prying. 2 days ago he congratulated me on 6 months.

When I accepted his offer I made a commitment to myself that I would do what was within my power to not let him down and not abuse the opportunity he's given me. I don't want him giving me this chance to have been a mistake. If I screw up now, I'm not the only one who will have to bear the consequences.
I can't cure my mental illness(es). I can't make myself smarter. But I can not drink.
It's not exactly a sense of duty or a sense of obligation or even gratitude. I'd say it's more a sense of loyalty. But whatever it is, it's the reason that this is by far the longest I've gone without a drink in the last 5 years. And 5 years from now hopefully I'll have my PhD and be able to say I did the entire thing without a drink.