I'm currently training for a sub 4 minute mile after quitting my college team and I'm having trouble with this girl I'm dating. I can't seem to keep my eyes off other girls and although I genuinely love and am extremely attracted to my girlfriend, I know I'm going to have to end things with then because I clearly still am wanting to sleep with other girls. What gives? Why do I suddenly want other hot girls badly when I have one already? Will I eventually be satisfied with one person a few years down the road, or will this be a constant battle? I also imagine my testosterone from constant training is making things harder, but any advice is appreciated. I feel like a piece of trash sometimes because my girlfriend would marry me if I asked her.