I see a lot of people say that they are in SP and it suddenly stops. Don't think you failed. Always assume you are dreaming. WILDs often start as False Awakenings, don't get discouraged by thinking you woke up, get up and do a reality check to make sure. Many of my WILDs start in a completely black and silent environment, as if I had woken up again and have my eyes closed.
Many times I have simply opened my dream eyes, expecting that it is a dream, did a reality check and found out that I was actually dreaming. If you have trouble opening your dream eyes without waking up, just imagine you are standing up instead of laying down. And look at your hands for stability while you create a door and walk through to get somewhere you want to go. Just a little tip I thought I'd share