Computer crash when overclocking

I have been trying to overclock my 4770k and i don't know much about overclocking so i just used AI suite 3. I set the desired overclock to 4.2 GHz. it works fine for a while, I can play games, I run a stress test and it doesn't crash. But if i leave it on over night when i wake up the following morning it either isn't on or its frozen. I don't know whats wrong, anybody have any ideas?

My computer specks

i7 4770k

corsair rm 750

corsair h100i

gtx 780ti

120 gb ssd for os

1 tb hdd

16 gb G.Skill Ares 1866

What is your mobo?

asus rog hero vi

What are the voltages and temps for cpu?

Voltages are probably more important if you are crashing when idle. 

your OC isnt stable, either lower the OC or increase voltage. 

We do need information like what voltage its at now, and what temps you have, like jon666 said.

Did you turn off C-states and other power saving features?

don't know much about overclocking so i just used AI suite 3

Thats your problem, dont use software to oc cpu's, I dont care what anyone says, AI Suite (& others) is a turd for overclocking - gives way more vcore than needed amongst other things. Learn and understand what happens under the hood. Do overclocking manually in the bios.

Follow a guide like this>

You will learn a lot about hardware in general with the above guide.

^^^^ THIS^^^^

This man is correct, the automatic overclocks always usually result in failure or a poor stability in my experience and from people I know who tried them. They make sense for a small overclock ie 10-15% but when you're really trying to push your chip, it comes down to being patient and ensuring you are getting the proper voltages/temps, while remaining stable when stress testing.

thanks everybody. im going to learn more about oc and do it myself