Glass half full

Everyone keeps saying must see life as a glass half full. You had a bad in day in office it could be worse, you have health problems it could be worse, you are going nowhere it could be worse, you could be starving. I agree with this point of view but it just seems to me that I would be justifying being happy by telling myself life could get worse. In yoga they say you must be detached from events happening in your life. You should not focus on things you cant change, accept that you are a small ant with a given set of legs and run with it, or crawl whatever is best suited for your body type or species in this case. I don't know how to get to that detached state, how to let things that make me angry go. How to enjoy the rest of my day by not focusing on one thing that's got me worked-up. For instance the monsoon came yesterday to mumbai, I should have enjoyed that, I should thought of having pakora with chai in the balcony. I mean what could be better than that. To take back control, to decide what emotions will enter my day. Doesn't matter what happens, I decide if I had a good or a bad day, not some arbit moron.