There comes a time in a project (especially the more ambitious kinds) where it suddenly seems like you've managed to overcome all the major hurdles, and it actually will be possible to complete the game. This is also usually combined with the stage at which the project starts to take shape and you have something nice to look at. It's a great feeling, and it occurred to me when I produced the screenshot you see here, for my still un-named game.
The only drawback is that it's usually soon after this point that there are no challenges left, and the rest of the programming is boring donkeywork with no payoff until the project is completed. This is usually the stage where I lose interest and move to something else. Not in this case though.
Maybe it's because it's my favourite genre (squad-level turn-based strategy game) and I've got the inspiration of Laser Squad and LSN to look at, and it's going to be multi-player, but I feel like I'm going to see this one through to the end. Then the challenge will be the hardest one yet - getting people to play it!