Comments :
Well yes I would like to have a few new things at a moment in hand and then try to gain depth in them, sorry to say but you can never claim that you are a master at a particular subject. There maybe some things in which you are at your best and it would be hard to compete you but that doesn't mean that you can't be defeated. My attitude asks me or makes my heart to study different things once I get interest in them. I am only into computers and programming or everything that includes Computers or the world of Finite Automation and discrete optimization. I am dedicated completely towards it.
Learning new things is actually very fun and a great way to spend your leisure time (at least it is for me). The ocean of knowledge is greater than GOD himself (I suppose even he doesn't have enough storage device to store all the information.). Also being the jack of all trades and master of none is a bad concept according to me as whenever I listen to this verse I remember a quote said by Albert Einstein "I don't need to know everything, I just need to know where to find it when I need it" and that's what I have followed in my life and will still follow but yes I won't stop learning new things. You may say that I understood this quote or interpreted it in a different way.
I know quite a few programming languages like C, C++ (GUI programming using Qt5), Java, these are my most preferred languages as I am good in them but not at my best as everyday I find a new way to explore an idea and a new way to think. Other than this I know JScript,VB.NET, python web designing, JSP (As server side programming) and at present learning Scala. So you see I am good in three but I still want to learn the others as I have developed interest in them and so I learn and study the rest everyday with a belief that within a few years I will be at my best in the above. On the way of me developing my skills I will definitely gain more interests for sure and will be learning them slowly but they will be added to my minds PriorityQueue with less priority and the above mentioned things have more priority.
Conclusion :
Learning new things are a different aspect and becoming better is a whole different aspect. New things seems very interesting but being consistent with them is quite hard as you will always find new interesting things which will force you to lose concept and interest in the subject that interested you before, which is bad imho. But if you gain new interest and stick with for sometime and getting to know it better then you will gain proficiency in many ways.
Learning new things and finding new interests is much more like that - "I want a new girlfriend everyday to sleep with or making my way to her p*s*y or try something new". If you want a new girl everyday then you must be rich, you must look like a hollywood super star, have a limo or a private plane, have a builder body etc etc.(as girls are most attracted to these things) but the disadvantage is that you may get AIDS and an EOF or better say EOL(End of life) tag will get itself attached at the end your minds doc or mind.exe or if all the girls catch you red-handed when you are doing your sorts of f**k with another girl. If you are caught red-handed then they will either kill you or all the girls will make you their s*x-slave. So it is better to be going along with a single girl, be dedicated be sincere and love her only (Occasionally if you get along with someone else then its not bad but she must have the same freedom as well.) now if she leaves you or you have problem getting along with her then leave her and find a new one. (Go to a pub and offer a beautiful lady a glass of Blackdog wine or Vodka, hahahahahahahahah)
(Above example is just an interpretation of my idea please don't get me wrong. All girls or women in HC if you are reading my reply then don't think I am a bad guy and I am insulting you'll, I am sorry if you get hurt.
So ultimately at the end I agree 50% with what @
Deque said but most importantly I would fall for your second thought more i.e. "Becoming-better-at-what-you-already-know".
Thank you,
Sincerely,
Psycho_Coder.