So please do apply self-discipline in your life. Having no discipline is like having a car with an engine that stops running frequently and won't exceed 2000 RPM.
Hard work does get easier in time, like working a muscle. And just like working out, you need to pace yourself -- approach hard work wisely and don't overdo it, even if you're enjoying it immensely.
I'm so glad my mom forced me to practice the piano - I wouldn't be the musician I am today without it... and I have no regrets about working hard at front-end web development. I owe my career in large part to the many hours I spent poring over JavaScript: The Definitive Guide and writing SPA web apps while others at my workplace were still using ASP and WebForms.