I've seen the film twice and I still don't fully understand the concept of Limbo. It is hyped up to be fearful, you can get stuck down there forever. However, we are shown on three occasions all you need to do to escape is kill yourself:
- Cobb and Mal run themselves over on a train after growing old -- why not just do this straight away?
- Soon after entering Limbo, both Adriadne (who is going there through the 'dream machine') and Fischer (who is actually dead) kill themselves to escape.
- Near the end where Cobb and Saito shoot themselves to escape -- again, why not do this when entering Limbo? Why wait around?
Am I missing something?