Sure, ājust doing the work anywayā is something that can be effective if youāve dealing with mild anxiety about not being good enough at drawing or something. But that sort of anxiety isnāt a mental illness, thatās just part of being human. š
What it sounds like @christopherh is asking, is: āHow does someone deal with a mental illness that significantly affects their ability to function, while working fulltime as a freelancer?ā
Sadly, I donāt think thatās always possible. If anyone reading this doesnāt understand why I might say that, then Iād encourage them to watch āThe Secret Life of the Manic Depressiveā by Stephen Fry. If you broke your hand, you wouldnāt be drawing until it healed. In a similar way, if you were experiencing a mental health crisis, your energies might be best put towards getting better.
That doesnāt mean that a having a mental illness would necessarily prevent you from creating excellent, meaningful work, or even necessarily from working as a professional. An example of someone with clinical depression who earned a living as a creative writer was Ned Vizzini, who was one of my favourite authours as a teen and sadly committed suicide in 2013.
I donāt know if I really have much advice, other than to be realistic about your limitations, and take care of yourself by working with a licensed psychologist.
Not everyone can handle the same pressures or an intense schedule. If you have a mental illness, you may need to alter your art goals to accommodate your treatment. You may need to develop your drawing skills at a slower pace, by working in bursts when you are able to do so, and taking breaks when you need to focus on your health.
A therapist would probably be able to help you deterime whether or not pursuing a freelance career would be a good idea when dealing with your specific illness.