I see the example sentences for the word "loss" here and there, and it sounds like that it is used mainly for referring to these two cases: In case that a great grief will follow up, like missing the opportunity to keep in contact with someone, or when someone passes away, and another case in which the topic is usually about money. I'm not sure if I'm right, but if I am, my question is that what word or phrase can substitute "loss" in cases that we're neither talking about a great damage, nor the topic is money. To shed some light on my question, I give an example:
My parents warned me that I mustn't become friends with him or else I'd make a loss.
Here, as you see, my parents are concerned about the bad influence that I might fall under, and the destructive effects that this friendship can have on my future. Assuming that I don't want to use the word "regret" do you think there's a phrase or phrasal-verb close to this meaning that I can use?