Overclock dropping speed

[Astrhate]

I overclocked my i7 7700k to 4.5ghz and was getting stable speeds for a few hours, but later i was dropping to to 800mhz.
should i dial back the overclock to a more stable speed or is there another reason it does't overclock that well

 

[nitinvaid20]

where are you checking those clocks? what are your System Temp?