You might set some intermediate goals such as riding 40 miles, riding 50 miles, riding your age in miles, riding a metric century (100 km, 62.1 miles) etc. As you accomplish the intermediate goals, you can give yourself a pat on the back and move on to the next one. As the trips get longer, you will need to pay attention to fuel and fluids. You can run out of gas on a bike (a/k/a bonk). You will need to experiment with the types fluids and foods that work for you and keep you going. Good luck. Keep riding.