When Juve got relegated to Serie B I was really pissed at them and Italian football in general. I tried to convince myself to never support this team again. Then one day, I was flipping through the channels and caught them playing against some Serie B side. I just couldn't change the channel anymore. Even though they were strggling, completely devoid of any genuine quality, disorganized, and playing unattractive football. I still couldn't see myself really cheering for anyone else.
I might enjoy Barca games, they are very entertaining and they do play the best football in the world. But even if I wanted to, I could not jump up to celebrate when they score like the way I did for Juve.
The way I see it, you don't choose who you wan't support in your life. They pick you.