I saw this quote by Steve Biko which said something like, the greatest tool of the oppressor is the mind of the one who is being oppressed.
The mind is powerful, the way we feel is dictated mainly on how we've allowed ourselves to think about something.
The more bad thoughts we allow to filter through our mind, the more uneasy we'll feel about a certain situation, and our feelings will be a huge influence on how we act.
You can tell yourself anything, if we choose to dwell on negative thoughts, our feelings will be negative and we'll react negatively to that particular situation we find ourselves in.
So that means that we have more power than we have perceived over life, and we're really not the victims of circumstances.
If something bad happens in your life, you can choose how it'll affect you. If you see it as a lesson which has given you the opportunity to grow and make you a better person, you'll feel good about it as you know that it was for your greater well being and self improvement. If you decide to dwell on the negative, you might think to yourself that you're such an unlucky person, all the bad happens to you, no good will come to you, and as a result you'll be down hearted, sad and even depressed.
If your partner breaks up with you, you can learn from how you contributed to the end of the relationship, and use this gained knowledge to improve your next relationship.
If the person was just naturally mean then you can tell yourself that God has a more suitable mate for.
So choose your thoughts wisely and you'll experience more peace in life. Change your mind and change your life.