How to know if you are good enough as developer ?

YES, you're good enough to become developer as long as

• Learn from your mistake
• Never satisfied, Never give-up
• Practice, practice, practice
• Remember that perseverance and passion drive effort, and effort drives achievement
• Aim for small achievable daily goals rather than Imaginary big goals without action
• Don't compare your self with other, your rival is your's yesterday self

Stop thinking that you're not good enough, even the greatest developer on earth (whoever he or she) start as a newbie, what make them better than us is because they learn earlier