There are ways to "ride smarter" rather than harder, too. They make a difference. Hills are easier when you get the hang of riding up them while standing. Also, pain while riding is not a some kind of badge of honor. Try to ride in ways that help you get stronger, but without pain and burning. Some of that may mean taking a look at how properly your bike is fitted to you, or not. Another part is learning which gear to use so you are not just grinding it out bloody sweaty bit by bit. And, try to engage your glutes (the big muscles over the back of your rump). Hint: slide back in the saddle, keep your back straight, lean forward as low as you can, and keep your feet pretty flat during the pedal stroke. Do not pedal so hard that your quadraceps (big muscles on the front side of your legs) feel any stress. You will go longer faster with less pain. But, when you finally get tired, you do not feel tired and yet you take some wickedly long naps.