The world is full of negative things, but it's how you handle them that shows who you really are. From someone who has been through a lot and witnessed a lot of things, I try to stay positive through it all. I've handled deaths of loved ones, a breakup, a long distance relationship, constantly being sick; but it's how I stayed positive and got through it all that defines my life.
I think with all the negativity in the world, it's important to stay positive. I like to think of myself as a "glass half full" type of person and I think that's an important way to be. Staying positive makes you and the people around you feel confident, and your positivity rubs off on them. Remaining positive through the ups and downs of life keeps you a happier person. I have been very low before and had a realization that if you put your mind to being happy you can just be happy.
Being negative about the bad things in your life or the bad things around you will forever put a damper on your life. In order to stay happy and positive in a low period, you must think and remind yourself that this negativity is not how you want to go about life. Life is too short to let bad or sad or frustrating or hurtful things get you down when there's always going to be something to help you get through it.
Another key to not letting negativity drown your life: surround yourself with people who are positive. Having positive and confident people around you who want to help you and want you to smile is incredibly inspiring and will make you feel like you want to be a better and happier person.
Staying positive is so important for your mental and physical health. When you let negative thoughts remain in your mind, they overwhelm both your brain and your body. They cause you to stress; they cause you to be unable to sleep or move and you are consumed by these negative thoughts. The best thing to do is look at any situation at a positive angle. If it's too hard, find someone who will help you find a positive in a situation. Find someone who radiates positivity and spend your time with them, become like them.
Exercise, talk to someone, eat a sweet food you've been craving-- do not lay in your bed and dwell on what's wrong. Negativity can take over your life, but you cannot let it. Stay positive through it all and you will become a better and happier person who can help anyone who thinks negatively, too.