Is language precise?

Some of my friends are terrific grammarians. I know this as I am the recipient of their forwarding to me all the correct uses of the words I mangle. Like that last sentence.

Ah me, clearly must have been ogling some unattainable jock during high school English class. Wonder what he is doing now? 

For me, it's trying to remember all the rules. 

I can work with some rules of course. Don't wear white after Labor Day, don't stare at a deranged person are two that immediately come to mind. It's the dire consequences of breaking those specific rules, I suppose. Really, you have to get the police involved, fashion or otherwise. 

So then, how to keep it all straight. And even if you use the correct tense, is that what you really meant to say?        

Reading the wonderful collection of short stories by Pam Houston, "Cowboys Are My Weakness" I came across this sentence which I thought brought this home; "When he asks you if you would like to open a small guest ranch…understand that this is a rhetorical question. Label these conversations future perfect, but don't expect the present to catch up with them."

Others that come to mind are "will you love me forever? I would if I could; I'll do it tomorrow." 

Correct usage, truth optional.