These tips are great, but the below will get you further faster...

Georegulus freelance guide

https://www.georegulus.com/the-ultimate-freelance-guide

Specific to motion design and super clear from a talented animator.

Freelance manifesto

https://www.goodreads.com/book/show/35386733-the-freelance-manifesto

A great book, really, really useful and probably an essential read. Some points prioritise making money over life, but I'd still recommend it.

Freelance jungle

https://freelancejungle.com.au/

Great podcast and community, focusing a lot on reducing stress and building support. Podcast episodes address a lot of common problems, highly recommend

Is this working?

https://podcasts.apple.com/gb/podcast/is-this-working/id1473508626

Podcast about work in general, but speaks a lot about freelance, burnout and common issues people have