In the video Sky says he wishes finding happiness was "as easy as buying a soda from a vending machine", but he knows that it's not.
"Unlike a maths test, there's no right answer when it comes to depression, but I know what it feels like.
"It's more than not being happy, it's more like you can't bring yourself to be happy."
"Depression is indiscriminate, it doesn't matter how much or how little you have in your own life - it can find you," he says.
Sky says he had a close friend who suffered from depression just like Robin Williams did, but he only realised the right words to say to that person when it was "too late".
Sky adds if he could turn back time he would say to his friend: "I'm not a miracle worker and I can't promise you much... I can't make the words go away, I can't make you love yourself...and I can't magically make you sleep.
"What I can do is wait right here with you until you are ready, we can talk all day, or we could be silent.
"We can do anything you want, as long as you know that when you leave this room, and re-enter the world, we're going to do it together, and I'm not going anywhere."
The video has gone viral and has been viewed more than 700,000 times on YouTube.
If you've been affected by the issues in this article, please call the Samaritans on 08457 90 90 90.
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