A day job to me is essentially trading time for money. It is usually separated into two broad categories. You can either choose to work for yourself or work for someone else. Both entails advantages and disadvantages that we should take note of. However none of these decisions should curtail your financial philosophy. There are frugalists, capitalists and frugal capitalists who are financially successful on both sides of the spectrum.
Being self employed often means being an entrepreneur. Property agents, stock brokers, insurance agents, freelancers and online/offline business owners are a few examples. The advantage of working for yourself is that you are responsible to yourself, Your financial future is in your own hands(some people might think of this as a disadvantage).
Most self employed jobs are self running "businesses" which means you will have to contribute your own CPF and health insurance. Scaleable business often means difficulty in starting up, difficulty in attracting customers/clients and difficulty in taking leave(crucial for some). Which would ultimately lead to the risk of not getting a stable profit, or worse incurring a loss.
Working for someone entails some stability. A decent company will provide you with your health benefits, contribute part of your CPF and give you paid leaves annually.
However, being employed under someone also means that that someone is in charge of setting how much your time is worth. Some people don't like that. The trickling down effect for salaries could mean that the top is making sure that he/she gets his/her fair share first before you.
A suggestion would be to join companies that does annual review and to have a benchmark pay for the job that you do(some people refer to salary.sg). To get a pay rise, you would need to climb the corporate ladder which means you would need to show/prove your capabilities to your employers. The pay structure is mostly linear and consistent annually, the direct opposite of how one earns from being self employed.
So no matter what your preference is, just remember to try to find the right focal point, before working hard towards achieving your goals.