How To Write A Handwritten Letter To Your Boyfriend . It’s okay to err on the side of cheesiness. Sincere lovers always appreciate the effort you put in writing the note; Write Love Letters to Your Spouse to Increase Your Connection from www.thedatingdivas.com “i can’t wait to grow old with you.” “my love for you will never end.” “you are my best friend and soul mate and i will love you until the end of our lives.”. In the end of the love letter, you can always add about exchanging love letters with your partner. What to write in a love letter to your crush.