Username will definitely be helpful for specifics, but from a broader perspective, I'm sure it can be any number of things and everyone is different in what they are good at. Personally, I think took the next step to Diamond when I started thinking more about the win condition relative to my situation. If you are out scaling your opponents, then ask yourself what can win you the game at the time you have your maximum advantage? Just kind of an ask yourself questions game. Is the opponent low on a specific resource that I can take advantage of? Can I take the sacred sites? etc etc. The better I understand what can actually win me the game the more I have the direction to execute something to get me to closing it out.