I am sure many of us have done it by mistake and accepted a random trade rather than click "update"
Luckily, I have never made this mistake and given someone 400 coins for 1 fish or anything.
However, perhaps there should be a one minute "grace period" to cancel that trade before it is committed.
The only way to do this, I guess would be to have a window made that lists all trades you have offered and accepted, some of which of you offered and are not accepted will be auto declined after 8 hours, this would also solve the problem if people are deliberately making trades to withhold others resources for 8 hours until they are auto declined.
Comments are accepted in this post if you feel different for some reason, but I believe truly this is a great idea