箐箐, i have similar conversations with myself all the time; thoughts about the meaning of life and the definition of success. i've been doing this for > 7 years and i can tell you that these thoughts are not helpful at this time. these conversations are you trying to minimize your cognitive dissonance. you're prehaps not living up to your expectations and so now you tell youself that what you value are perhaps not so important. i'm not saying that one should not ponder about life but perhaps not now when there's so much going on inside of you.
btw, success is a function of happiness, period. it doesn't matter how you live your life, the key to makes sure that you're happy with your life. i mean be truly happy with your life. happiness is a function of a bunch of things and the weightings vary with people so what is happiness and what is success? they're different across individuals! the question to ask is, what is it about life right now that i'm not happy with and what can i do about it?
i guess i understand what you're going through now. i have hit rock bottom before; nothing went well and i felt like i was helplessly watching myself fall apart and at the same time felt so aloof it almost felt surreal. i went from an A student to someone who graduated with a GPA that's barely 3.0. you have no idea what i had to do later to redeem myself. i don't know when you will snap out of this lethargy but it will pass sooner or later. in the meantime, try to do some damage control. take up more responsibilities but don't overwhelm yourself. obligations can force you to at least do something.
all the best.