To stop you from checking emails when you are not supposed to, think about the following.
Are you checking because you can take a meaningful action or out of curiosity?
If knowing the content of a mail now changes the way you act (compared to what you’d do if you would check at the appropriate time), that is a meaningful action.
In all honesty, there are very few cases where this is true.
Our opinion is not stronger if we share it now or tomorrow. Hearing some feedback is not going to make us change now, and probably it won’t tomorrow. Checking now if that email we have been waiting for has finally arrived is not going to give us a headstart on tomorrow’s work.
More often, it’s curiosity that drives us. It’s the dopamine hit we get from knowing something, even though it does not affect our possibility to do something about it. It’s like scrolling your social media timeline out of boredom.
We can train at keeping that impulse under control.