No, you are not going crazy. After a separation, there is a lot going on in the brain, and understanding the neuroscience of heartbreak will help you realize that feeling sad after a breakup is natural.
Love is not a limited resource. You can have many different kinds of love, with different people. One is not better or worse, the dynamic is always unique in its own way.
We must not give away our power, our light and not let any of the past harm the future. We must get back up each and every time, and still approach the world and relationships with hope, love and softness.