It should be no secret at this point that I am a fan of Luke Smith I don't necessarily agree with everything he says (since it is impossible for someone to be a copy of another person) but he of course says a lot of insightful things on a variety of important topics. If there was one video of his which I believe that everyone should watch it is the one titled: "Pessimism is *literally* for losers." It is so great that I stole the title.
I, like Luke, am sick of seeing and being around pessimists. Luke explains that pessimism convinces people that doing nothing is the absolute smartest thing that they can do. Do the following statements sound familiar to anyone?
All of these statements are statements inspired by pessimism rather than rational thought. A pessimist has no ambition since they have convinced themself that any effort that they put into anything will ultimately be in vain. This sort of mindset is bound to lead to depression as it is impossible to live a happy life without working towards any sort of goals.
My favorite verse of scripture reads:
Wherefore, whoso believeth in God might with surety hope for a better world, yea, even a place at the right hand of God, which hope cometh of faith, taketh an anchor to the souls of men, which would make them sure and steadfast, always abounding in good works, being led to glorify God. 
God wants us to have hope, pessimism takes us farther from Him and farther from true happiness. Even if you don't believe in God you should be able to recognize that hope is something that we all should have. Faith without works is dead  and really it is impossible to accomplish any works without faith which comes from hope which is killed by pessimism.
The other bad thing about pessimism is that it is contagious. If you are being pessimistic you are doing a disservice to those around you. The absolute last thing someone wants to hear when they tell you their goal is that accomplishing their goal won't benefit them (unless of course their goal is to sit around watching porn or something all day, in that case you should tell them to get a life). If you are a pessimist you are a drain on your friends' lives, fix yourself so that they can better enjoy your company then seek to remove other pessimistic influences from your life, if that means temporarily distancing yourself from your friends do it and tell them why you are so that they can have a chance to change. The news is also a large pessimistic influence, they want you to live in fear if you watch and read it and buy into what they are selling you will become a pessimist, get that garbage out of your life.
Anyways I'm starting to ramble. This is one of those topics that is so important that you feel like there should be a book written on the topic but it would be impossible to do so because the message can be effectively communicated in just one page. Pessimism is for losers, don't be a loser, stop being a pessimist.
 Ether 12:4
 James 2:17