A "thing" is just such a vague and general concept that is useless. If either your job or your relationships can be reduced to only mastering 1 thing I really envy you. If you say I am being unfair and of course it involves many sub-tasks , so why dont just choose to be good at life? So you can concentrate in just one thing and still have 2 other "things" to spare.
Now, less snarky and more serious, in any activity or discipline you choose, there are people who are dedicating their whole life to it, so you have 3 options.1) Hope your natural talent will compensate the less hours you dedicate to it (this is almost always false). 2) Accept you will never be as good as the crazies who spend all of their time on it.3)Join the fray and invest all your time on it.
Almost all great creations in humanity, things like Einstein's theory of relativity, Dante's Divine Comedy, Egypt's pyramids are the result of incredible and exclusive dedication for many many years.