My main motto in life as been Shit happens, but over the years I have added to it. We all go thorough life trails and tribulations. We sometimes get more than we deserve in the shit department but more often than not we get through it.
When people get through a tough time or terrible event, something wonderful always happens if you have the right attitude; you grow. Life is about expansion and growth, learning about ourselves and discovering new things about the world. However, there are many out there who don't want to grow and expand. That is fine, but they will be the ones that will find life hard and sometimes unbearable.
I am not saying that one should be happy and positive all the time, that is is almost impossible. Having an attitude towards how you deal with the shit that happens. For me, after years of practice, when #shithappens I process it quickly. Take in what has happened, go through any grieving stages that one may go through and then grow from it, learn from what happened so I don't do it again, or now know what to do next time.
This process has many steps and several different psychologists and therapists have listed them in countless articles. In order not to repeat what the professionals say, I will leave a link to a couple articles that describe each in more detail. There is no real right or wrong way to deal with shit especially because it is unique to you and your own situation. By understanding and knowing that there is a process that you can practice to a point that it is second nature, you will see a huge difference in life itself.
I love life and I have become so used to my process ( stop, have a few moments of panic, relax, think of what is the worst that can happen if it goes bad, think of solutions, leave the situation if possible for a few minutes to focus on something else, and realize it is what it is, and move on if a solution has been made) that I sometimes am accused of being aloof of the situation. Now that doesn't mean that it is immediate, sometimes it takes hours, days, or weeks depending on what the situation or problem is.
Positive thinking doesn't mean that you don't let the bad in, it just means you know shit happens and then you take that shit and grow a garden of beautiful flowers.
Articles about Healing processes
https://wakeup-world.com/2015/10/21/5-powerful-steps-to-emotional-healing/
https://www.psychologytoday.com/us/blog/crazy-life/201504/the-6-steps-healing-you-need-know