How to USE a business bank account (Eenmanszaak)

Dear fellow expats,

I searched quite a bit but still can't make it clear, so please let me post my question here.

I have just registered with the KvK as an “eenmanszaak” and opened a business bank account.
Now I am wondering how to use it.

I guess I shouldn't use money from my business account for personal expenses such as everyday meals, detergents, towels and clothes, but then for what purposes can I use it?
(I'm a programmer if it matters, so the foods or clothes etc. will never be related to my business)
What about rents or phone bills?
If I use it in a wrong way, is there any penalty?

This might be a stupid question but I hope someone can answer it.

Any advice and suggestions will be appreciated!