Asking for a letter of recommendation from a professor who's witnessed my breakdown I'm currently applying for an intensive language program, and I've taken courses with a professor whose letter of recommendation would likely carry a lot of weight– he speaks the language fluently, and has spent years studying the country. His course is also the only one I've taken that is directly relevant to the language program I'm applying to. 

However, I'm not sure if it would be appropriate to ask him for a letter of recommendation. In the first course I took with him, I did relatively well; I got all As on my assignments, but I rarely spoke with him, and never really stood out. 

The second course I took with him (the one that's relevant to my language program) is what worries me. During that semester, I had a family emergency/mental health problems, and, after multiple meetings with this professor, I ended up receiving a G grade in the course (meaning that I have to submit the coursework I missed by the end of this year). He's seen my outlines for the essays I owe him, and he's admitted that they're pretty much perfect– but I haven't submitted any actual essays. However, we've spoken at length about my family emergency/mental health issues, and we've grown somewhat close (he also has had some experience with mental health issues). I feel like he understands why my work ethic suffered, and doesn't seem to hold my delayed coursework against me. 

So, my question is: should I ask him for a letter of recommendation? I feel like his recommendation would go a long way on the application, but only if his recommendation is actually a strong one. Despite his understanding of my personal circumstances, I'm not sure if my coursework has been good enough for him to feel comfortable giving me a glowing recommendation. I also don't want him to feel pressured (out of, I don't know, pity for my situation) to give me a recommendation letter. Any advice?
I've had students ask me for letters with some wording along the lines of "if you feel you can write me a strong letter."  From what you've said, it makes sense asking him for a letter, but you might consider this approach: 

First let him know that you're interested in this program and see what he thinks about it.  If he's very supportive of the idea, then you should have nothing to worry about asking for a letter.  If he's not, you could ask for other suggestions.  (And even if he thinks it's a good idea, he may suggest some other other opportunities as well.)