The reason its best to attempt a Wild after 3 - 4 hours of sleep, is because your more likely to do something known as "REM Rebound". REM Sleep is when you have your more vivid dreams, (the REM stage occurs around every 90 minutes) so attempting WILD when your close to, or right after the REM stage, will allow you to much more quickly jump right into a dream, which means less time spent trying, and by extension, you should be less likely to get bored of it and give up.

So, if you can, try to wake up after 3 - 4 hours, and then attempt WILDing the same way, and see if you have anymore success.