Keep in mind that people generally don't hop on a bike and start doing 20, 30, 50...miles their first time. It's a progressing of improved fitness and body adaptation that happens over time. Set goals and work towards them. Most of all, be consistent. That doesn't necessarily mean riding every day, but keeping a regular schedule that you put as a high priority helps it become a new lifestyle, not just a task to accomplish. Also...have fun!!