I need some advice on what to say about quiting my job...?

I just recently went through a really bad break up that has put me into a funk and isn't letting me do my best at work and school. Since I am a student first and foremost, that is what my main focus is and between work, school, and my therapist visits - I am not able to give work and school my all - I just don't have the time. So I am deciding I need to quit my job to be able to handle everything that is going on with me right now and focus on my cles. How should I go about telling my boss this? He is in his office right now in a meeting but I want to tell him when he gets out.. any suggestions? He also knows what is going on with my break up and how I have not been myself for the past month, he has brought this to my attention.