The true beauty behind Brazilian Jiu Jitsu is it's ability to allow a person to see and feel personal, physical and mental growth. I personally have felt all these things in my journey and have witnessed this with many of my students and training partners.
At first you shall not succeed (in a great way). It is very humbling stepping on the mat for the first time. The physical exhaustion is like no other, using your body in ways you never have before. We all fear the unknow, the new. To top it off you suck at everything! But have no fear if you continue your journey and hit the mats magical things happen. Bringing so much power to your life you didn't know you needed.
Watching students learn techniques and implementing them in action is so satisfying. Something that used to be the impossible is now one of their favorite techniques. The physical transformation is a perk of jiu jitsu, using muscles in ways they have never been used. All these things together create such mental strength. Creating a feeling within, the knowledge of our body awareness, the process of learning, the mental strength is what makes jiu jitsu so powerful. Stick with it no matter where your journey is, remember this YOUR journey.