The first time I heard the cliches "Love yourself," "You can't love someone else if you don't love yourself first," etc., I didn't give them much thought. Of course I love myself, who doesn't? And even if I didn't, that doesn't have any bearing on how I treat others.
I now think that these statements mean more than emotional masturbation and trite self-help affirmations.
First, understand that who you are today is not the same person you were 10 years ago, or yesterday, or even 10 minutes ago. The person you will be when you wake up tomorrow is a different person still.
Consider how you treat someone who you love. I will expend extra time, energy, and even money to improve the life of someone I love. This isn't because I'm a generous and selfless person. I value certain relationships because of reciprocity; a person who I love has made my life better in the past, and I expect them to continue to do so in the future.
On the other hand, if there's someone I don't know or who I don't value, I will not necessarily go out of my way to help them. If I dislike the person, I might even gratify myself now even if I suspect it will cause them inconvenience or pain now or in the future.