Laptop does not wake-up from sleep

I am using dell inspiron 15 and windows 8.1 .

Here's the problem.
Whenever my laptop goes to sleep either by itself or by pressing the sleep button 
It never , ever wakes up no-matter whatever key I press or click .
It stays in the sleep mode for ever .
I tried this couple of times and waited for an hour to wake it up but it never did , lastly I had to long press the power button to emergency switch-off

From then I have tried my level best to avoid it from sleeping,
I have changed the power options to "Never Sleep" because sleeping for it equates to dying ultimately .

Any help or suggestion is welcome.