Categorical imperative

<p dir=ltr>"Act only according to that maxim whereby you can, at the same time, will that it should become a universal law." </p>

I have for quite a while already lived by this philosophy, although admittedly, it is a difficult task. On one hand, I do think that this is the right thing to do. I mean, how could you do anything else? Do you really want to do something less than the best possible? Do you consciously want to avoid to do the best you would be able to do? Doing less than the best possible, is by definition less than good, or non-good, which its to say in colloquial terms, "bad". Do you want to do good or bad things? <br>
On the other hand, deciding what is the categorical imperative is a difficult task. The principle assumes that you know the right answers with certainty. How many things do you know with absolute certainty? I can't claim that I know many, yet we all have practical lives to live with an infinite amount of small decisions, we have to make choices even when we do not know the categorical imperative. For one, there are just too many choices that we could find the best possible choices to every one of them. But much worse, there are questions which land in the grey zone in between where no absolute rule can be defined. For example, consider the question of where to put the balance between freedom of speech and security of the individual. It is trivial to find examples where rigorous application of freedom of speech puts individuals in danger of life. Still, it seems clear that freedom of speech is a really, really important feature of civilized societies.
On a trivial level, how would you set the categorical imperative in the question of which route to take when walking to they office? The fastest, the nicest, the one where you might meet that nice person in whom you're interested in, the one which fits the weather, the one where the risk of getting mugged is lowest or the one with the fewest blue houses on the way? Claiming that you should choose the one that fits the situation best means you're avoiding their question. Or perhaps an even better, even more trivial question? What is the categorical imperative to which apple juice to drink in the morning? Supposing that the price, ecology, and taste is they same? It's just a too trivial a question that you would want to spend energy on finding the absolute answer, the categorical imperative to it. It's, like, who cares?
And that demonstrates the problem. In our everyday lives, we have just too many problems, too many questions that we could afford to spend the time to find the categorical imperative to each and every one of them. Conversely, demanding the categorical imperative to every choice, "which hand to use for opening the toilet door?", would paralyze us, make us unable to do the most simple tasks in life.
Perhaps the conclusion, the categorical imperative,  would then be that the mental effort should be saved for the important questions. Questions such as, "when to take up that difficult topic with your best friend, which is already hurting your relationship?" are the kinds of questions where you should find the categorical imperative and also act accordingly.