There's a lot of pressure in the spiritual community to think positively, and to create your reality by choosing happy thoughts. So let me say this first. There's no doubt that your outlook affects the way you move through the world. If you believe that people are mostly good, and that being alive is an incredible, albeit sometimes heartbreaking experience, that's going to inform the way you interact with people, approach new situations, and challenge yourself to live a life that feels good to you.
Conversely, if you think that you can't trust anyone, and life is brutal, that will also affect the way you move through your days. But no matter your outlook, not everything in life is positive and light.
You can only know what you know, right? You have your frame of reference. You've been loved, you've been hurt, you've been cherished or abandoned, or abused, or whatever the case may have been. And your experiences affect your outlook. Maybe you were taught that your feelings didn't matter. Or that love was conditional, something you had to earn in order to be worthy of it. Maybe you learned that people will hurt you or leave you, or that your safest bet was to make yourself invisible. You do not have to accept as fact, everything you've been taught. You don't have to believe everything you think, as the saying goes.
My point is, if your "default setting" is that life sucks, and you suck, and people suck, I'd really look at that, because there's no doubt that's an outlook that will weaken you, and it's also based on lies. Knowing yourself, which is at the heart of any spiritual practice, is really the thing. Understanding the way you're thinking about things is essential, so you can cease to feed a critical, unforgiving voice, if that's what you've been living with inside your head. I know about that, because I lived that way for many years. I teach yoga and stream my online yoga classes around the world, because I was able to heal through my own practice, and I'm passionate about sharing those tools. Learning to feed a loving voice so that it grows and strengthens and follows you into every aspect of your life is the biggest game-changer I know.
So yes, much of our suffering comes from the way we're thinking about things. And there's enormous power in choosing one thought over another. Still, not everything in life is positive. Suffering doesn't come only from our thoughts. Some things, in actuality, are devastating. And this is where I become concerned.
When a person is in despair, few things are more alienating than being told that s/he is supposed to think positively. I cringe when I hear someone say, "Everything happens for a reason." You know, maybe everything does happen for a reason, and maybe it's all random, and maybe it's some combination therein. That's a question people have been grappling with from the beginning of time. The truth is, none of us will know for sure what happens after this until we exhale our last breath. No point arguing about it in my view.
Regardless, when a person is grieving, they do not want to hear that this knifing thing has happened for some reason they'll understand someday. If you lose a child, for example, you'll never understand that. That will never be OK. That will never go into the category of, "Thank you for this experience."
If you're physically or sexually abused, that will never go into the "Thank you" category, either. And suggesting to people that they ought to be able to be positive and grateful in every moment lacks compassion and understanding. When you ask people to deny their experience, to push down their real, complicated, raw, and immediate feelings, you also ask them to cut themselves off from their own intuition. You're plunging them into further darkness.
If you're enraged, be enraged. Figure out why, of course, examine it, but allow yourself to feel your feelings. The same goes for grief, jealousy, fear, shame, guilt, doubt, and any other "shadow" emotion you're likely to grapple with at some time or another. This is part of being human, this is how we learn and grow and open. Anything you repress, deny, or run from will own you. It will chase you down again and again and again.
Devastating heartbreak can close you or open you. When you allow it to open you, you become one of life's more insightful people. You can be grateful for that. If you choose, you can use your experience to help other people going through the same kind of despair. You can be grateful for that. If you survive abuse, you can be thankful for your strength in choosing to unhook your journey from the violence that was perpetrated upon you. You can be grateful that you've chosen to identify yourself as a survivor and not a victim.
If you've lost someone you'd give anything to hug, you can be grateful that you loved so deeply. Life is full of everything. Some of it will break your heart and bring you to your knees, and some of it will take your breath away with its beauty and fill your heart with yes, and thank you. In my view, being spiritual means you hold it all. You don't deny your reality, you face it. And you work to keep your heart open. That's a practice that's available to everyone.
I wouldn't try to chase happiness; I did that for years, it's what we're taught to do. Be hungry for the truth of your own experience. There's a lot of peace and power in that. Wishing you love, and the strength to hold it all.