Jumping to conclusions/acting on assumption is, or can be, based on two things: a lack of information, and/or moving beyond the boundaries of whatever you're making assumptions about.

By that I mean, one can make assumptions because they don't have enough information about the situation at hand, yet act anyway.

I think the problem with such circumstances is that it actually takes a lot to apologize after jumping to conclusions. I know this better than anyone because I am stubborn as a mule, especially when I was in high school. That Turkish blood, it runs in the family, haha. Anyways, apologizing about jumping to conclusions means admitting you were wrong about something, which is difficult for lots of people, and the reason I think lots of arguments and conflict occur.

So, when I jump to a conclusion, and somebody gets mad at me about it, I think about that. Nobody wants to have someone angry at them. It feels like a personal attack, even when it isn't, so it's easy to lash out, even if you're the one that made the incorrect assumption. But remembering that it's difficult to apologize, then apologizing anyway, makes me feel a lot better about the situation, and myself. It's also, I'm sure, lowered my blood-pressure, and has made me much calmer of a person.

As an addendum, this whole process can be more difficult online, where information is permanent, and communication that isn't face-to-face leaves much more room for assumptions to be made. It's the whole reason /s exists.