Practice is necessary to develop the skills required to pursue music successfully. But practice can also be a crutch - a delay tactic. Just as many people continue their college educations to avoid the necessity of getting a job - of facing the real world. It can be the same in music. You're "never" ready. The fact of the matter is : you're always ready. When you can struggle through one song, you're ready!
As in most things in life, it's important that you strike a balance between practicing and performing. By performing, I don't mean a huge concert venue. It might be a performance for friends or relatives. It could be at a coffee house or an open mike night. Anything that puts you in the position of having to play songs - original or not in front of people is valuable.
Songs are not exercises. They are vehicles of self expression through music. This often strikes fear into the hearts of new performers. This is an understandable reaction. Remember that fear can be redefined as excitement. They have the same physiological symptoms - shaking hands, a feeling in your stomach, the tendency to run. But if you enter the arena of performance, these feelings will ultimately turn to motivation.
So, practice and perform. Make it a lifelong habit!