I met my classmate and he wanted to go with me. I don't want to associate with him. How can I refuse?

I can see that you are a little disgusted with this acquaintance. If you have no friendship worth cherishing, just an acquaintance, then stay at a respectful distance from sb. Reject all his requests and suggestions. Don't be vague Procrastination will only give him an excuse and a chance to get close to you again. Since you don't feel well, don't fraternize. You don't have to break up with them. You don't have to contact them as long as you are usually fine. I think this is the best way to adopt it.