How to stop being afraid of selling something?

For example, if i have to sell my used Iphone, wich is in good condition. I sell it for the BEST price and i don't cheat on people when i sell something. But still i get really scared! I feel guilty, like i'm cheating on someone to buy things from me, even if sell it really cheap, just to get rid of it!(i'm not doing any business just selling my own stuff)

So i start shaking and being really nervous. So the seller might probably think that i'm cheating on him, that thats the reason i'm so worried!

I don't know i just feel guilty and feel myself bad. That someone gives his money to me. That's crazy! What do i do?

You are probably afraid of rejection. But remember if someone does not want what you are selling they are rejecting the product and not you as a person. You might try rehearsing your sales pitch with someone you know a few times to get past the awkward speaking parts.