Hi, I'd like to help you with your question.
Getting angry easily usually indicates a background where you were either exposed to others who were angry a lot as in domestic abuse or you were abused yourself. People are not born with anger issues so you learned these feelings from someone.
You mentioned that your mother tells you that you are hateful. Do you have a good relationship with her or are you at odds? Is there a past history between you that is negative? I ask because her opinion could be based on her point of view, which may not be a healthy one.
You are assuming that if you become more friendly and kind to others that you will lose your ability to perceive any mistreatment differently. But becoming nicer does not mean you lose your ability to see others for who they are. Being nice also does not mean you have to expose yourself to others for them to take advantage of either. If you had a childhood where boundaries where not respected, then you would easily confuse being friendly with being taken advantage of.
There are different kinds of nice. Some people equate being vulnerable with being nice. These people see that being open about themselves and allowing others to take advantage of them ("of course you can come on vacation with us and not have to pay for it") is a way to be liked. It is the only way they understand. Boundaries are an issue for them because they never learned to put them up and draw the line for personal space.
The kind of nice you are referring to is a social nice. Being friendly with others, talking to them and generally being helpful is not leaving you vulnerable. You are being polite but not allowing the person into your life. You have ample opportunity to get to know a person before you open yourself up more to them so you do not have to worry about being taken advantage of.
Some of the ways you can protect yourself include:
Learning to say no- when you can be comfortable saying no, you take away anyone's ability to take advantage of you.
Trust your own instinct- you will know when someone wants to take advantage by the way they act. A change in voice pattern, the way they ask, how they act (suddenly they are so nice to you when they were normal before), etc. People know when they are being taken advantage of.
Recognizing when you are being used- you have your own internal alarm system. Most people learn to either ignore it, or they misuse it because of a background that damaged it, such as abuse. Learn to listen to warning bells going off in yourself. Once you can get in touch with that feeling, you will be quick at spotting someone who is taking advantage.
When you meet people, have things you are willing to talk about already planned. Most people will talk about family, jobs and general topics like opinions about the weather. Keep your topics at this level until you have had a chance to get to know a person. Then move to a deeper level but not too far. Your feelings about your job, talking about your other friends, etc. This is usually deep enough unless the person becomes a best friend.
Keep in mind that everyone at some time in their lives gets taken advantage of. If you can see it as a learning experience, you can use it to help you grow stronger.
I hope this helps,