Never leave the person who understand you more than anyone else. Someone who you can talk to about everything and will stand next to you even with your unwanted attitudes. Treasure the one that accepts and loves every bit of you.
This is true in relationships and also pertains to moving, having to say goodbye to family and friends, making a career change, saying goodbye to old habits/lifestyles,etc. Be Brave enough to say goodbye and life will reward you with a new hello :)