Read The Joy of Living: Unlocking the Secret and Science of Happiness by Yongey Mingyur Rinpoche. It will answer all your questions about meditation, how and why it works, what method is the best for you, etc. You can buy it here.
It's a great method for loving yourself and for understanding that all people, just like you, want to be happy and want to escape the pain. So it will make you more open to others. If you have hard feelings to someone or even hate them, it will definitely help you.
Here you can read a good and easy description of this method.
If you want someone professional to teach you this method, just find some meditation teachers or groups in your area.
Concentrate on your negative emotion while meditating and soon you will understand that you can't concentrate on it for too long and it often happens that you start thinking about your laundry or something like this. This way you will understand that all your feelings and emotions are not that powerful and you can control them if you watch them. You can use this method on the go if you are too busy for formal meditation.
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