Then you have the politicians they say "Yes we can" and then after a while they realize they can't because there is the opposition which says "No" to everything which seems to be a good idea. Others promise "Yes I will make America great again", forgetting that we are not in the wild west anymore and immigrants are not welcome at all, before they needed it to win land, kill the natives and look for gold, but these times are gone. That's the same with "Yes" I am for the Brexit, forgetting that the UK is all alone without its Commonwealth and therefore there is no common wealth anymore and we all need each other.
Since I was a child I have learned that it is better to say "No" first, think the question over carefully and change your mind into "yes" if convenient. That's far better than to change a yes into a no. That doesn't sound so good.
Saying "yes", the opposite to "no" is far easier. No problems, no discussions, no fights with yes ! and the opposite of course with "no". Therefore those who want to stay always in peace with everybody and agree to everything, they should always say "yes". But please note that it can be dangerous !