If you want to write a love letter to your loved ones then the procedure of writing a love letter is not the same as writing a professional letter or like writing a Letter Writing Guide. The love letter should be interesting and lucid. The love letter should contain your emotions and it should be written from your heart and soul. The love letter should show your feelings which must be natural not artificial. The love letter should be written such as when the reader reads it, the emotions and feelings of your heart should flow out of the letter.
You should not think that the beginning and ending of the love letter should be interesting but you should think that the whole letter should be written interestingly so that the reader does not feel boring in any part of the letter and keep their interest in reading the full letter till the end.
The content of the love letter should not be just a matter of fantasy but the base of the letter should be somehow factual. When the love letter is written on the base of truth and trust, then the relationship will be long lasting.