The biggest mistake I see guys make is when they don't even want to hear what the trade offer is. Sometimes it would be in your best interest to be open to trade offers !!
Maybe.
But..... probably 99% of the time that I've been offered a trade, it for something that I have zero use for or interest in. If I traded, it would mean that I then have to go through another cycle of trying to sell whatever I just got instead.
Just takes a lot more time and hassle to get to the end result that way.
The only time I've offered a trade was when somebody specifically posts that they want to trade for the exact item that I just happen to have laying in the corner.