A very interesting promise is made by Advaita Vedanta --
This might seem very silly to most people, but this promise is very profound and has great depth to it. What does "attain what you already have" mean? It means you are already Brahman/Atman. There is really nothing to attain per se. The attainment is merely a dropping of the veil that seemed to hide your true nature. After the veil drops, you realize you were already and always that which you realized
What does "give up what is not yours anyway" mean? It means the world of objective reality, where you are a doer of actions and owner/possessor of things becomes apparent as just an appearance. So you give up the idea of being a doer and possessor, because you never were a separate actor or owner of "things". They were just appearances that rose and dissipated in you, the reality.