I know I love someone when I miss them when they are not there - constantly being aware of their absence, when I feel warm at the thought of them, when touching their skin is more fiercely addictive than breathing, when the slightest disappointment for them feels like a grievance that I must avenge, when the thought of their disapproval curdles my guts, when the sight of a smile on their face brings light into my world, when I see that love reflected back at me - seeing them loving me and seeing me loving them, when I trust them with my life, when I know that whatever happens we will stay being us, when they feel like the most precious thing in the world.
Love can be genuinely awful. Worse than the norovirus on a coach trip. When it goes wrong - and it usually does - it kicks a hole in your ribcage and voids its bowels in your soul. Get burned badly and from that point on, falling in love is like inviting a werewolf into your home: you sit there fascinated, watching it eat at the table and admiring your curtains. You make conversation and share private jokes. But try as you might, you're not quite relaxed and you're not quite yourself; you're on tenterhooks, aware that any moment now it's going to turn round and bite your throat out.