Well, as for deciding on what someone will enjoy doing, it is important to understand the extremely fuzzy words of "degree" and career".
A degree is simply a piece of paper that opens the doors for certain occupations. A particular degree is required for certain occupations, optional for others, and mostly useless for everything else.
A career is actually a word that is slowly dying out, at least under the current conditions, thanks to corporate hiring and “cleaning” practices. A career involves staying at a particular type of occupation for the long haul, and usually implies staying at the same company.
An occupation though, is what the person does in order to occupy their time in order to make money.
There are three general types of occupations.
Straight pay: You work for someone else, for some sort of fixed pay, each year. These types of jobs are the ones that predominantly require degrees. Additionally, the higher your fixed pay rate is starting out, the higher your credentials will need to be, the jobs also get progressively more difficult and/or boring. The ones that don’t require degrees in this category pay almost nothing.
Commission pay: You work for someone else, for some sort of fixed commission, each year. These types of jobs are a mixed bag as to whether they require a degree, but many of the occupations on commission pay pretty well, since they usually require something a degree really indicate very well, the ability to market/sell something. The more complex jobs generally require a degree/certifications.
Paying yourself (not to be confused with saving): You work for yourself, the pay is completely variable each year. Working for yourself rarely requires a degree unless you are practicing a profession. Lots of people love the idea of this, but can’t really practically pull it off without some sort of backup. For those from a wealthy family, they have the backing of their parents, but otherwise, it usually requires some sort of cash reserves or a fallback occupation.
I am an engineer, but only have it as a degree, it helped me move on to bigger and better things. As for occupations, I am only 24 and have probably worked at 8 or 9 occupations, a different one just about every year after I could drive. The first ones were boring, somewhat physically taxing, and low pay. The middle ones were just boring, and somewhat low pay. The latest ones have been fairly interesting and good pay. My next step is to move on to something really interesting with very good pay (working for myself, at least mostly).
To be specific my occupation list went like this: lawn mowing à caddy à astronomy lab assistant à shoe salesman à data tester/data input/computer repair à database management/hardware engineering à special type of law/learning finance and safe ways to invest
My next steps are going to be (most likely): entrepreneur/web development. These will be in conjunction with my latest fixed pay occupation. I may also do a small amount of real estate.
The best way to reach FIRE quickly is to put a high premium on your time, doing things purely for the sake of them being fun/easy will generally directly conflict with this, at least when you are starting off. I only say this to counterbalance all the advice you will constantly get to enjoy life, which you should.
) naively thinking I could arb, take advantage of the nyse specialist step-in-front rules to steal pennies on low volume stocks, and use Dijkstra's algorithm to exploit inefficiencies in currency pairs (e.g., you walk usd->yuan->yen->usd and come out ahead due to short term market inefficiencies - in practice I just made the broker rich and often got stuck in a broken circuit). 
