I've learned some hard lessons in my life. So, this is the wisdom I've been passing on to my children — in an age appropriate way, of course.
We live in a ruthless capitalist society.
When push comes to shove businesses don't give a shit about the well-being of their workers if it interferes with the company's ability to make a profit. Managers and business owners hide behind tropes of professionalism — don't talk about your wages with other employees, stay loyal to the company and it will take care of you, always give two weeks notice or more when leaving, etc — as a way to cover their own greed.
Know what the market rate is and ask for more (“competitive wages” are bullshit), always negotiate your salary, talk to your coworkers about your salaries, loyalty goes two ways, always keep your resume out there, don't stay at a company when a better offer comes along, job hopping is a legitimate way to get what you are worth, two weeks is meaningless when businesses can fire you for no cause at the drop of a hat.
TL;DR — Fuck you. Pay me.