Friendships we keep won't be all rosy till they fall to the law of diminishing marginal returns and eventually fading away. They're like the sea, sometimes calm, other times tormentuous. Whichever ways, we share stories and memories, celebrate gains and wins, work on our weaknesses and defeats. There's always and will always be an activity at every period of the friendship.
You tell your friend stuff and do stuff together with the foreknowledge that you're in it together. In your vulnerable moment make no mistake, you may be in it alone so careful what you let out to your friend. There may have been no "we" but "I" from the very start of the friendship but only that you did not pay little attention to see that. A lot of friendships of late are inspired by "isms"- each person with a different view coming to the table with different objective(s). Call the friendship the table on which a deal is struck with each person hoping to achieve their objective(s). Be vigilant at this point not to lose guard because the race with narcissistic instincts are at play at this stage.
They will snitch on you at any point if that means satisfying their narcissism and achieving their objective(s). No boys boys or girls girls code can save you from the snitch sword. Sadly, such snitches has the stitches to your wounds but won't give them up. Their snitch swords and lying tongues would come cutting from all angles like Bayern Munich players queuing to put 8 pass Barcelona.
Don't you ever make someone regret being your friend and telling you stuff. The person told you all that you know now because he/her trusted in you. So don't thrust the trust to another trustee because your friend is unaware of that one(the third person) or better still could have gone ahead to tell him/her in person.
Make friends, as many as you can. But police yourself against as many friends as you can.