[Coder-san]

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.

The verb-usage of "master" was taken in my post from the figure of speech "Jack of all ..." I didn't literally mean that.
Besides since we cannot truly be perfect/best/unstoppable at something, I prefer to understand mastering something simply as being "professional" at it. Able to challenge anybody in the world in the specific field. However, the outcome is irrelevant.