How do you plot your stories? I figure out what's going to happen to my MC. Usually that's not good. I don't want them to have an easy time of it. They have to plan how to defeat whatever problems come their way.
The pressures of time constraints, force characters to do what needs to be done. My novel Seventy Two Hours is a book that lasts that long. Actually a little longer, because the epilogue happens two months later. You definitely don't want your characters having all of their life to make their decisions. Wouldn't that be a slow moving read?
Put your characters in as much trouble as possible. Ramp up that tension. Tight. Restrain them. Do everything you can to hinder their chances of a happy ending. Your reader will love you for it.
Make sure that all forces work against your characters. That's good reading. And a book worth writing. :)