There's some great advice in both (IMO).
Essentially, I think a Person's thoughts creates their "reality." And their actions, and then their results. And this has been understood for hundreds of years. "What a Person passionately thinks, they become." [Proverbs 23:7 "As he thinks in his heart, so is he."]
Many People miss out on a great deal of wisdom and understanding because of their preconceived notions/beliefs. They think they've got it all figured out when in reality there is still much to learn.
Anyway, LOA is just one "Law" of The Universe, if you like. There are several more: Including "The Law Of Compensation." That is basically defined as: "You will always be compensated for your efforts and for your contribution, whatever it is, however much or however little."
Then there's "The Law of Action."
If you aspire to be a successful Marketer/Entrepreneur and and/or reach financial freedom ― and beyond ― you must take action. No matter what "The Secret" illustrates, it won't just happen by thinking about it.
As it's been said: The Law Of Action states that: "You must do the things and perform the actions necessary to achieve what you are setting out to do." So take action: Take massive action. You can't get "something" for "nothing" ... And you will enjoy more satisfaction and fulfilment by working for your goal(s).
Then, when you combine that with LOA/"Think And Grow Rich" tools (like Affirmations, Visualization, Positive Thinking, Vision Boards, etc.) you will be significantly closer to reaching your goal(s)