I've been a successful freelancer for 10 years. I still feel like I should always be chasing my next opportunity. The author (not pictured) has been a freelancer for nearly a decade. Luis Alvarez/Getty Images When I became a freelance writer nearly a decade ago, I assumed the uncertainty would eventually fade. I imagined there would come a point where I'd built enough relationships, landed enough recurring clients, and published enough work that I'd finally feel secure. But that moment never really came. Today, I make a stable living as a freelance health and fitness writer. I write for major publications, have long-term editorial relationships, and often have more work than I can realistically take on. On paper, my career looks stable. And yet, I still approach my work as if I were trying to land my next job. Part of that is practicality. Freelancing teaches you quickly that stability is often temporary. Editors leave. Budgets shrink. Publications pivot. Consistent work can disappear overnight.…