Is the cup always half empty or half full?

The other night a friend and I were talking and he joked with me and said (looking at my empty water glass) so is it half full or half empty....I laughed and said, neither it is empty.  Those words came back to me today.  Last night I got sick with this yuckiness that has been going around.  And then this morning I woke up to a freezing house.  My furnace had stopped working.    I tried everything I could think of to fix it and prayed for it to be something easy and cheap to fix...But, it would not work.  I went out to get new batteries for the thermostat as a last ditch effort before I had someone come out to look at it and frankly I was just about in tears.  I told a couple of people what was going on and followed with, "I cannot seem to catch a break ever..."  Followed by, "But, it could be worse....furnaces can be fixed."  And that is when those half full / half empty words came back to me.  I almost always follow bad news or something negative with something positive like, "it will get better" or "it could be worse", or "at least...."  I think most of us do that.  Someone dies and we say, "Well, at least they are in a better place."  We lose our jobs and we say, "Something better will come along."  We break up with someone and we say, "It's ok, there are other fish" or "There is someone perfect for you waiting out there and now you are free to find them."  My question is...is it ok to just say life stinks sometimes?  Can we just say, "My cup is empty right now, period"?  I don't have the answer.  I always feel bad when I complain.  I try to laugh about it and smile it off...but is it ok not to do that sometimes?  We all know people who complain all the time and are generally a drain to be around.  I don't want to be like that, but is it real to always have a smile on your face?  Is it real to always put a positive spin on things?  I just don't know....I am going to have to wrestle on this for a bit.  I would love to hear your thoughts on this!