There's no being 'good' at yoga, it's all yoga practice, or even better- yoga maintenance!
One of yoga's many lessons teaches us not to get hung up on what we can and can't do, and not to let our out practice become achievement orientated. Everybody has a yoga body, and all our yoga bodies are unique to us.
Often what brings people to start yoga in the first place isn't the same thing that keeps them coming back. Just like ourselves, our practice is constantly evolving and changing, and whatever brings you to practice on any given day, is to be nurtured and respected.