You have to find a way to keep the game as interesting and fun for yourself as it is for the players. GM'ing shouldn't feel like a chore, and if you're enjoying it, it'll translate into the game and make it a less enjoyable experience for everyone.
The more freedom you give your players, the more you have to be adaptable to the unexpected. This seems obvious, but a lot of times players are going to come up with some stuff out-of-left-field that you'd never thought of. If the game needs to follow a certain path at times, you have to be willing to guide your players in the right direction, or flat-out force them to. This is 'railroading', and while it has a (sometimes rightful) negative connotation, it's necessary in certain types of games.
Realize that the game will most likely end inconclusively, like 95% of games do. The best thing you can do is review your game for what worked and what didn't, and apply that in the future. If you really like the idea behind the game and don't want to abandon it, restart it with improvements based on what you learned.
Figure out a way to deal with players who can not keep up with the pace of the game, especially in larger games. I don't like leaving anyone behind, but it is unfair to have 6-10 people waiting for days on one or two other players. It would be helpful to everyone if you include in your game's Original Post how often you intend to update, whether it be daily, every other day, each week on a certain day, etc.