Stress wasn't something new to Leonardo. That feeling has become a constant in his life since he was fifteen, when the war with the Foot Clan began, or even before that, taking care of his siblings. So he had to find ways to cope with it.
Meditating, spending time with friends and watching Space Heroes were his favorite options–Until you came along.
By spending time with you, Leonardo found even more opportunities to relax, and surprisingly for him, physical contact was the most effective. So it became normal to you to deal with a kissy, cuddly and clingy turtle. Which bring us to the present.
You were in your boyfriend's room, lying on his bed after patrolling New York. He was spooning you with his eyes closed, occasionally kissing your shoulder softly. After a few minutes of silence, you heard him murmur. "I love you"