infinity, randomness and insanity
There are 2 things that will impair your mind and eventually drive you insane:
Infinity: A novice math student is literally playing with infinity since the subject matter is so vast. To maintain his sanity, he must either have strong internal aesthetic guidance or a good external advisor.
Randomness: A businessman or a trader in a well established market with extreme competition is playing with randomness since all sources of possible profits now have unpredictable origins like political unknown unknowns, global demand imbalances, interest rate and exchange rate fluctuations etc. (i.e. There is no more space for innovation or value creation.)