What is phrase "como se va"?
I think it is: ¿Cómo te va?, ¿cómo se va? is weird, even in the sentence "¿Cómo se va tu día", in that case I would say "¿Qué tal tu día?".
Actually, I was thinking and the question ¿Cómo se va? could be used to address in the formal tú to someone asking him what's the transport he uses to go home or other place, in example:
A man is off working and a work mate asks him ¿Cómo se va?, he can answer in two forms, telling him the exactly route that he takes to go to his destination, or just the transport he takes, like by bus, by car, by subway, etc.
Obviously the informal form for that question, which you would use with a close friend or family is :¿Cómo te vas?.
We use it a lot after working or after school and often with the intention of seing if the routes of both persons match in order to go with the other person together.
I have not heard this particular phrase used before in Spanish but from my existing knowledge of Spanish I would say it is likely to be:
¿Cómo se va? = How are things? (Literally: how goes it?)
A much more common greeting would be
¿Qué tal? = How are things? o ¿Qué tal estás? = How are things with you?
Are you sure you are not mixing it up with the french: Comment ça va? which is a colloquial way of saying: How are things or how are you?
I hope this helps
I checked with a native speaker and it is a little strange. More common to say... ¿Como te va? How are you doing?