Log in to your ChainEX account.  

Then go to your profile and click on Personal Details. 

From there, go all the way down until you see Deactivate Account. Insert your password and click on Deactivate my account now. 

You will then receive an email to confirm that you want to deactivate your account. 

Once you have deactivated your account, you can reactivate it anytime you wish by simply logging in again.