This quote is about how our thoughts can affect our actions. "The body achieves what the mind believes" means that if we think we can do something, our body can actually do it. Our mind is like a powerful coach that helps us do things we want.
Imagine you're trying to ride a bike. "The body achieves what the mind believes" is like saying if you believe you can balance, your body will try harder to stay up.
In simple words, this quote tells us that our thoughts are important. If we believe in ourselves and our abilities, our body can do amazing things. It's like having a strong and positive mindset that helps us achieve what we want.