"Scenario: You run into a poorly-timed automatic door.
Negative person: "Stupid fucking door. I bet the engineer was a fucktard that lives in his mom's basement."
Positive person: "(laugh audibly) Wow! I'm an idiot. Haha! This'll be a great story to tell my kids!"
I know the latter seems really cheesy, but it makes everyone else more comfortable. If you are laughing, they can laugh with you. They appreciate your reaction and it brings a smile to their face. The former leaves them with a sour taste in their mouth. They don't want to smile at you or even look at you because they fear that they are being judged.
Scenario: Spiders freak you the hell out.
Negative person: "I hate spiders. They are vile creatures. I found one in my basement the other day and I killed it."
Positive person: "Yesterday a spider snuck up on me in my basement. I flipped shit. Screamed like a little girl and ran to the other side of the room. I stood there, frozen, staring at it. Then the little fucker chased me down! I had to run upstairs and get my mom to have her get rid of it."
The negative comment sounds dismissive and violent. People will be uncomfortable sharing things with you for fear of you being dismissive and "killing" it. The positive one is entertaining and relatable. Everyone is afraid of something and sometimes has to have someone do something for them, even if it's embarrassing. They see that you shared with them, so they may share with you.
The most important thing is friendly laughter. Whether it's at yourself, at the world, or at your misfortune, laughter is infectious. If you bring joy to others, they will want to return it. I've never made a friend when I was being negative. My friendships always start when I laugh at myself."
http://www.reddit.com/r/offmychest/comments/1cbepj/i_have_practically_zero_friends/c9fcl0e