How can I overcome over-messaging?

I'm usually a chilled out person, but when people are important or special to me, I tend to become overbearing.

My first example is a girl I've loved for over a year, I failed to give her space (and still am) I keep on messaging her because I don't want to let go of her in my heart. I tried deleting everything of her, all The ways of contacting her, but a few days later, I couldn't stand it, we'd been talking for a year and I didn't feel right letting go like that, I havent resolved anything with her. Now, even though she never replies, I message her on Facebook again -_-

Secondly I have a friend whose cat recently was put down and I message her every day to check up on her... I'm worried about becoming an obsessive messages again, I lost the love of my life, I don't want to lose another friend.