You can look to so many smaller things as to why we lost this game. KG was horrendous on the offensive end as was Ray for the majority of the game. Injured arm or not, Rondo HAS to make that layup at the end of the game. The last play at the end of regulation was just pathetic.
But in terms of the big picture...the celtics did everything they could to hold on. They fought and fought but the fact is, the Heat are just better. They're younger, more athletic, and just...better.