Passion: If you're a cyclist it's like breathing. It's just something you have to do - daily (or as much as possible). It's not about the bike. Hey, didn't someone say that already? It's more about the lifestyle. It's how one approaches their daily walk through life - how one eats, sleeps, rests, works, and plays. Everything affects quality of life and the process of preparation to function at one's highest level.
Healthy balance: Physical and mental health are integrally connected. Each benefits the other in non-quantifiable ways, present and future. This is probably the most important reason to ride or to stay committed to any exercise program. It's a bonus, a gift, a blessing to find an activity that you're naturally drawn towards. Honor and nurture it!
Attitude: Very connected to one's health. When one's health is good usually the attitude is good too.
Outlook/perspective/clarity improve dramatically: In some strange and mysterious way, the cosmos line up and one understands his place, his station, his purpose in life when the clutter of an unhealthy lifestyle is moved aside. Praying for guidance is also of paramount importance.
Positive stress release: Way better than drinking alcohol and binging on comfort foods. The endorphin buzz is the purest and healthiest form of addiction. Take it from a recovering alcoholic.
Integrity: Self-esteem, self-worth, one's "home-grown" identity transcend society's definition of success based on one's financial status and outward appearance.
Discipline: Paradoxically, the benefits described above outweigh the pain, suffering, and discomfort that very often accompanies the act of riding. It's true that sometimes it's just not appealing or easy find the motivation to climb on the bike. Unfavorable weather conditions, time of day (after work), illness, other commitments can make it rather discouraging. That's when one has to remember and evaluate what's really important - the benefits always trump the temporary emotional and physical unpleasantness of the moment.
Pleasure: It's natural that we all seek pleasure. American media is very effective at promoting the bling, the glamour, the thrill of a pleasure seeker's lifestyle. But let's be realistic here. Much of our daily experiences aren't exciting or filled with the highs of riding a rollercoaster. I think it's rather rare to feel ecstatic. This must be why people turn to drugs over and over again. They're chasing that elusive pipe dream of that first high the fastest way possible, however destructive it may be. Personally, I rather enjoy the more subtle and natural approach to a healthy high that only a vigorous workout can provide.
Sacrifice and surrender: I believe this is healthy and natural to do on a regular basis. If you're not doing something that benefits someone else or a larger cause other than your own pleasure-seeking addiction, healthy balance and perspective are impossible to achieve. Christ was the master of this and has proven once and for all that it's the only way to be. Cycling is sacrifice in a way. It's not easy much of the time, and often downright painful. But it does promote the "Pay it forward" mentality that's good for the planet and those we come in contact with daily.
*Environmental: These days it's ever more important to be conscious about the carbon footprint we all leave behind. Oil spills, depletion of resources, souring economy, ever-growing traffic jams, overpopulation: it's important to do something personally to be part of the global solution and less of a contributor to the problems of consumerism. Being a schoolteacher, my bike is parked daily in the classroom. The kids understand the car is not the only way to get from A to B, even if B is 35 miles away.