Definitely your mindset has to do with a lot of success or failure and good for you for getting out there and getting your own independent clients!
I, too, am a freelance writer. I’ve been freelance full-time for over a year and a half and I have been making the same or more than my previous full-time salary the entire time.
I hate Upwork and Fiverr. I personally feel that these types of sites perpetuate the vicious cycle of going for the lowest bidder and looking at quantity over quality, while also bringing down the average for all the great writers out there.
If you ever need the info, here are a couple short pieces on how I find most of my clients (I make $5k per month or more every month from freelancing alone).
Hope they are helpful!