I don't know anything with certainty, but seeing the stars makes me dream.
我不知道世间有什么事是确定不变的，但只要一看到星空，我就会开始做梦。
From Loving Vincent.
By comparison with uncertainty, I like certainty better, but I know life is always changing, the world is always changing, and this is an age full of uncertianties, opportunities, risks and crsis.
And the only way to ensure an invincible position in the competitive world may be to become stronger and smarter.
Don't indulge in dreams, get up to finish some useful works.
Jack of all trades and master of none.
门门精通，样样稀松。
Being a jack of all trades doesn't mean you are a master of none, because learning is not a zero-sum activity, you will be rewarded in some way for everything you've learned, maybe the benefits present themselves in some imperceptible way.
And in many cases, knowing a little of everything can often be better than having one expert skill set, and if we can grow up into a generalist, a real generalist, or take a multi-disciplinary approch, we still can obtain some great achievements.
Just like learning programming languages, if we can keep learning those new languages, we would have some different but beneficial understandings about the language we have mastered.
But we must notice that if we can master some skills, the common features of them will help us a lot in learning new skills.
Refine the skills we have learned, make them better, but always try to learn something new.