I suppose someone should come up with a version for guys?
You may not be her first, her last, or her only. Most likely, she's loved before, and she'll love again. But if she loves you now, what else matters? She's not perfect and neither are you. The two of you will never be perfect. But if she makes you laugh, at least once makes you think twice, and admits to being human, and making mistakes... hold onto her, and give her all you've got. She's not going to quote poetry, and she's not going to be thinking about you every moment, but she will give you a part of her, a part that she knows you can break. Don't hurt her, don't try to change her, don't expect too much from her. Smile when she makes you happy, cry when she makes you sad, and miss her when she's not there.