The right approach and the right mindset is to make trading a part-time job that is useful to supplement your income from the main job, and even if for example you manage to become a fairly professional trader by always being able to make a profit or when you are already in a situation where your profits are greater than losses then I think at that time you can think of a new plan, you can quit your main job but on the other hand you also have to build another place that can provide you with income such as maybe a business or other things that can provide a fairly certain profit.
You're absolutely right. Maintaining a main job while trading on the side is a practical approach.
Keeping your main job ensures a steady income, which safeguards your ability to meet basic needs without the pressure of needing constant wins from trading. It's a wise strategy to treat trading as a supplementary income source until, perhaps, your trading profits are consistently outpacing your losses.
Of course because as I said above that trading is a part-time job and not a job that can provide the main income, because the main income is something that can always give you a guarantee in a certain period of time that you will be able to earn money or earn, while trading has a level of risk that sometimes cannot be avoided completely and this is why I think the better decision and approach is to make trading a side profession to supplement your main income.
The downside of making trading a priority to earn or making it your only job is that there may be times when you need money for living expenses that cannot be tolerated while you are losing money in trading. As you said, the purpose of maintaining a main job is to ensure that our needs will still be met without having interruptions when you experience losses in trading, or simply even if you experience losses in trading but you still have a main job that will be able to provide you with income to make ends meet.