From one person leaving an unfulfilling job to another doing the same, I feel you.
I'm 54 and leaving teaching after 20+ years in higher ed and theatre-making to pursue an art/illustration career. I gave myself two years of prep, and this last summer between academic years was a good dunking in the growing pains I'm going to experience.
It scary, but I have a supportive partner and that makes all the difference. He went through a similar career transition when the bottom fell out of journalism and small periodical publication. So he knows it takes time. But the two years notice I gave my work has really helped me (and them) and everyone else I know come to an understanding that the end is nigh. And that has generated a bit of optimisim and lots of expressions of hope and interest in what I'm doing.
The biggest challenge I'm experiencing is having the patience with myself to understand just how slow the development of a career in the art field can be. What was an appropriate window of lead time to buckle down and make something new of yourself is much longer now--significantly longer than even 10 or 15 years ago. Every step forward is in constant flux... For example, 10 years ago book editors might have received 1000 queries a month--now some say they sometimes get 10,000! Big Social media has not only changed the game but is also changing itself. Covid also changed everything.
So just be prepared... Have your plan and follow through, but be prepared for growth to take much longer than it used to. There are many many exceptions to this, to be sure, but be prepared to ultimately need to make your own path. Examine where the advice you are listening to comes from with a critical eye, as their experience will rarely be yours. Take what you can and forge what's right for you, and be willing to try to play the game especially at the beginning.
We're all finding our way. And each step can feel hard-won and not enough at the same time. I'm still getting used to that ironic duality myself.