I had a uncle who was lost when his love of his life passed on many years later.
He wrote me a letter on how he felt and I was surprised as I only met him once when I was only at the age of 16 yrs old.
In the letter he wrote that she was the only one for him and they were friends,lovers,partners for life.
They talked about things and got on well, so compatibility with temper type,interests,
views on life, views on marriage, respect for each other,sharing and working as a team .
They were both soft spoken people who never had to raise there voices as they truly cared about each others feelings.
I have met lots of couples whom married high school sweethearts and are still happily married.
Can’t say that for all though.
“Know thyself” then look for someone with similar characteristics.