How can one deal with intense attraction to another student, and constant thoughts about them, coupled with the fear of the relationship developing for the worse, anxiety about rejection, and the desire to befriend them or collaborate with them on work?

What happened to this young man is a form of forbidden infatuation, and a Muslim should not attach his heart to ephebes. Whoever falls into this must restrain himself from what Allah has forbidden. Following one's whims is a serious matter and a gateway for Satan. Allah says: "O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - indeed, he enjoins immorality and wrongdoing. And if not for the favor of Allah upon you and His mercy, not one of you would have been pure ever, but Allah purifies whom He wills, and Allah is Hearing and Knowing." The advice is to completely avoid this young man and stay away from his friendship, and if necessary, leave studies at this school and move to another, then do so.