I was told the same thing and it is absolutely not true. Careers in the human services field, like teaching are especially underpaid. I do think it is good advice to do what you love, but if you are concerned about income, you might want to direct your passions in the direction of a viable career. For instance, if you love the visual arts, you might want to get a job drawing ads for a corporation as your day job, and then do the more creative stuff on the side. That ensures you have income and you also get to be in a field that is related to what you love. Hopefully your creative stuff will take off and you can eventually quit your day job and focus solely on your art.
I was always told the opposite, "Make money and you will be able to do what you love". The truth is somewhere in between.
That's what my physics teacher (who is a millionaire and teaches only because he enjoys teaching) tells us. If you're smart enough and work hard enough, you'll make money so then you can do what you want rather than worrying about making enough money. Of course, if something you love is also something that pays well, you're really lucky.
The thread title isn't true without caveats. Not at all. I think it's more appropriately applied to maintaining motivation over the span of your working life. The motivation needed to get your butt out of bed every single work day to go make that living. So much easier if you enjoy your work. People also apply themselves more readily to a task they enjoy because it doesn't feel like work. Therefore, better, more natural chance of making advancement.
(My general advice is more along the lines of: If you want to be happy, don't get caught having to spend significant parts of your working life doing something you dislike. Even if it's lucrative. An overabundance of money will bring a certain freedom, yes. But that won't satisfy the deepest parts of many people later in life if it's something they hate doing.
And channel your coinage correctly. Save it up so that you have options, so that you don't have to do things you don't love most of the time or when you are older. Avoid mindless consumerism. "Oh, you needed those shoes in all three colors?" *concludes person is silly/brainwashed by marketers/insecure/wasting their life*)
I think the counsellors are just trying to help you find yourself. Do what you're naturally meant to do. Such as, an istp is a good mechanic. Don't pick money first, because you won't be happy. "Do what you love [are naturally meant to enjoy and be good at], and the money will follow [you will naturally be a good competitor, and possibly become great, and of course, be rewarded monetarily]." They're just trying to guide in the right direction, not solve all of your practical problems lol......They didn't say "do what you love, and you will get rich". I suppose it just means you can make money doing what you love, not necessarily get rich.
I've found that there is some truth to it, over the years.
"How dreadful!" cried Lord Henry. "I can stand brute force, but brute reason is quite unbearable. There is something unfair about its use. It is hitting below the intellect." ~ Oscar Wilde - The picture of Dorian Gray
I think both ways are about the same. One you take out sleep and necessary chores from the time you have in a week, you'll have about the same amount of time at work as you do away from work. Work does take up the part of the day that is most valuable, though, IMO. You could do what you don't like to make money and enjoy the time you do have (work to live) or only do work that you enjoy and hope to find a way to get paid for it (live to work and enjoy it). Chances are you'll have less money for the time you're not working.
Ultimately I think the solution is to not couple your love and enjoyment with money, because there are diminishing returns on the pleasures money brings (trust me on this one) while working because of love is something you enjoy every time, which is sort of what I think this advice is trying to get at.