When making a coaster, always have a vague idea of how you're going to end, and keep it in mind when making your coaster. You don't want to make so much track around the end of the station to the point that you make it impossible to end.
An easy way to do this is to make a little bit of track coming out the back of the station first, before you start out the front, so you always have the visual there of where you're going to end.
