You don't need to remember all the lines in the P&L.

You need to protect your bottom line.

My 6 steps process for you:
a) Understand what is your Gross Margin for your brand / SKU
b) Divide it by the HL (beer) or Case (Spirits) you sell
c) That's your GM/HL or GM/Case. Learn it by heart
d) For every marketing investment you want to do, divide that number by HL or Case
e) That's your Marketing/HL or Marketing/Case
f) Do c) - e): If that amount gives you a NM that is too low, you are hitting your bottom line.

Keep your brand afloat.

Gross Sales is what you tell your friends.

Net margin is what you put in the bank.