How will we know whether we think right or not?

I'm the type of person that likes to see everything from every possible angle and perspective. So that means that I can actually agree and disagree from every angle...but you see I have people who tell me how to see life differently. Some see it as life being full of opportunities, and hope. Others see it as being full of people who will always hurt you and use you no matter what. They tell me life's a bitch and then you die, that simple. But you see, i refuse to see it this way. How will i know who's right and who is wrong? What influences me into believe in the way that I do? I do believe life is full of opportunities and chances and with a little hope anything is possible. Although I also believe its true that people always use you, it might not be intentionally or in a cruel way but they always want something from you, its how the world works. Somehow even people you love and care about always end up hurting you in some way, they might break your heart, betray you, loose your trust, walk away from your life, there's different ways people can hurt you without it being physical. And the saying "Life's a Bitch" well, yeah it is but you shouldn't see that as a downer, or see it as a bad thing. The way i see it is that life just throws challenges at you, battles, risks, its like a game. Its up to YOU whether you want to win or lose. Its up to YOU on how you approach the situation and with what perspective and attitude. Its up to YOU who you want on your "team" and what "strategies" to put into action. Life is a paradox...its complicated but simple at the same time. It just depends on how you see it. I'm still skeptical of the issue on people being able to change or not. It might apply to some people but not everyone entirely. Some people can change but a lot there's just no way that they ever will. I rather not get to in depth with that topic....but i will in another occasion. Just remember that the only person who can tell you what to do with your life, how to do it, and how to think, well that's only YOU.