A male colleague of mine has been getting particularly close to me lately, but I know in my heart that he is going to study abroad in the future, and there may not be any long-term interactions between us.
This colleague is quite generous at work, often inviting the team to dinner and taking the initiative to help me deal with some trivial chores. Sometimes, he would talk to me privately to share his confusion and ideas at work, and also valued my suggestions, feeling like he took me as a trusted confidant.
Although I'm in a single status, reason tells me that we're on different paths in life - he's planning to study abroad and I'll be continuing to work at home, so it's hard to have anything in common in the future.

I often don't know how to respond appropriately in the face of this particular friendliness of his, not wanting to misunderstand his intentions, but also not wanting to appear aloof.
To be honest, anyone in life longs to meet someone who understands them, even if it's just a simple chat. These actions of male coworkers, such as eagerness to help and private exchanges of heart, do tend to make people think more, which is actually a reflection of trust and understanding.
If we were in a different scenario and the other person was a female coworker, we might naturally develop a BFF or comrade-in-arms relationship; but if we had a family of our own, we would also treat them as workplace allies. But the situation at hand will inevitably trigger some ambiguous associations.
As my friend analyzed, "I'm single but know there's no future because he's leaving the country and I'm at home." Can we actively avoid thinking emotionally? For example, in a relaxed tone of voice, "Dude, I know what you mean", or jokingly give him a blank stare back "Thanks". Just treat each other as purely heterosexual friends.
The beauty of the Chinese language is that the same sentence can be interpreted in many ways. And we are often only willing to interpret in the direction we expect, which is actually human nature.