While there are countless external reasons for strengthening your core - a flatter belly, a six pack, looking svelte on the beach - the most important reason of all is to build internal endurance.
Physically, having a strong core is essential to a healthy body. First, it helps you to support the alignment of your skeletal structure, to maintain good posture and to stave off back pain. On an emotional level, internal strength is key for confronting life's inevitable challenges: with a strong core, we are able to remain centered and calm in the midst of crashing worlds. Spiritually, a strong core is a great foundation for many forms of seated meditation, which require practicing stillness for extended periods with a straight spine.