This positive resignation letter is due to marriage and relocation of the new family.
Dear Mr./Ms. Bossname
It is with mixed emotions that I tender my resignation from (company), effective (date).
I am sorry to be leaving such a vital and innovative company. However, my departure is due to my upcoming marriage and a big shift in my life. I will be relocating to (place) to accommodate my (husband/wife)'s job. I am excited to be starting this next chapter in my life, but I will greatly miss my time spent here.
Thank you for the opportunity to be part of (company), and I wish you all the best.