Why do people say one thing and then say something totally different later?

So aggravating....My spouse will say one thing and then say the complete opposite later. Ex: We were talking about getting a second home, as a vacation home, so we found one that we both agreed we liked and were talking about submitting an offer. He began telling me how "we have been talking about this for sometime now and we knew we were going to do this eventually". He was all excited and talking about what a great deal it was and didn't want to pass it up. Let's do it he says!Later we were with some friends talking about the home and he says "We are not buying a home in that area." I was shocked. I mean how could he say one thing to me and then amongst friends says the opposite. After a week passes we meet with a realtor and submit our offer.....The next evening we have a disagreement about something totally unrelated and he tells me "You pushed me into signing that offer, I told you I did not want to it". I have told him several times that if he felt uncomfortable in any way that we did not have to make an offer. Seriously, I could take it or leave it. I am just confused as to why he is constantly taking back what he says.