(A continuation from last post...)
I probably abuse point 4 slightly, in the sense that sometimes I stay up late, I probably don't eat as much as I could, and that I don't exercise. However, none of these are ever because I'm "overworking".
I stay up late because I usually wake up later than normal (day starts at 9am for me). I can always eat more thanks to my genes, but I'm not gonna cook a 2nd lunch and dinner because that's too much work just to start gaining some weight (I'm a slim build). As for exercise...I'll concede I have no excuse. I'll probably ride my genes on that one till my metabolism starts slowing down too much and I have no other options but to burn off any belly formations.
However, back in University I was exactly the same - which was a stark contrast to many of my classmates. Constant all nighters, stressful weeks, and skipping breakfasts were completely common among them and something that personally blew my mind (particularly skipping breakfast, as even when I wake up late I usually have a small breakfast before lunch). Freelancers (or freelancers-to-be) need to keep their health above all else. Yes, there will be an occasional late night for your client, or some busy weeks, but with proper scheduling and discipline you do not have to suffer consequences for them.
Point 5 nails it. Client focus is indeed what freelancing is all about. You take your skills to serve others. Use your knowledge, your experience, your professionalism to help clients and companies, help them be a better business, and they'll love and tell everyone about you. Fairly simple.
Final point is a key to a freelancer's sustainability. As a web developer, designer, or illustrator I have to keep up in all 3 areas or I'll get left in the dust by new freelancers (keeping in mind of course, that there will always be people better than me anyway). Web is a constantly moving target, design constantly evolves, and illustration is a skill you build over a lifetime. Constantly improving yourself with client work or even in your free time is a must.
In conclusion, the article is pretty spot on. Freelancing is a fun journey, and I'm glad there are many sites out there helping out the new ones to start off on the right foot.