I believe most people are honest and show at least some level of empathy. We help each other to achieve better things.
Then there are few people who do not look at you as a person but rather as a mark/asset ready to be exploited. They even come with silver tongues, masters at lies and deception. Sometimes you’ll find many with a short period of time. But don’t make the mistake of assuming this represents people as a whole - don’t let these few self centered people define your world view.
There is absolutely no benefit from stressing about it so don’t. All we can do is plan and screen the best that we can then sometimes roll the dice. Most/all of us have been fooled/snookered at least sometime, and chances are it may happen again. Don’t beat yourself up either. Don’t live in paranoid fear.
It’s easy to get angry when somebody wrongs you, but I try to understand the root cause to better to deal with them and is better for my mental health. I look at the world as endless potential wealth. If we came from huts, clubs, caves, where did all this stuff we enjoy come from? But some people look at the world as having limited pie slices, so they better hustle to get theirs before someone else, sometimes using decent. Often they think in terms of lack, glass half empty than half full. Something in their life programmed them to think this way, often negative.