Marriage is compromise. When two neshamas join to form one, both need to give up some of themselves to create a new, peaceful unity. This is the message we see from very early on.
During the Bris Milah ceremony, the following is declared
“כשם שנכנס לברית כן יכנס לתורה לחופה ולמעשים טובים”
“In the same way that you entered the Bris, so should you enter marriage, Torah and good deeds”
Just like during the Bris, the moment of connection with Hashem, we lose something – a part of us is cut and taken away, so too when we want to create the relationship with our spouse (and so too with Torah and performing good deeds which need sacrifices) we need to make sacrifices and cut things out of our lives which will not help the relationship for it is only by losing do we really gain!