I Was Sent to Another World to Protect an Unfriendly Princess

I was always held back, despite how talented I was, no one ever recognised me. On my way home, a tragic accident occurred. After, I was reincarnated in another world, except the goddess was beyond useless. This was my second chance. I was brought to the other world to protect Lucia, a mean, sharp-tongued princess, who was meant to be the next ruler of the land. She didn't accept anyone else, why did she accept me? Why is it that I have forgotten all about my past? Have I lost something truly important to me?