Intent

It's so easy to know why someone did or said something. At least we think it is.

For example, "they said that to make me look bad" or "they did that to show me up".
We think we instantly know another persons intent behind their words or actions.

But it's not that easy. Even if you consider yourself intuitive. Intent is extremely hard to know.

Consider this, sometimes we don't even know why we've done something. How many times have you asked yourself "why did I just do that?" or "why did I just say that?". And oftentimes we don't have a good answer for our behaviour.
Knowing that, how much harder is it for us to judge the intentions of someone else?

Most people act in good faith. So assuming they're out to get you, or they're out to cause problems is usually the wrong assumption. Plus it's a horrible way of living. Why spend your time figuring out the evil intents of every other human being? Just worry about your own intentions, that's enough of a chore on its own.

Of course, don't be naive. Being taken advantage of isn't a good thing either. But it may be better to be taken advantage of the odd time rather than living in a negative state assuming the worst about everyone.