You can't, all you can do is be the best person you can possibly be, be happy, be confident in yourself and that you have value. Don't let your friend's indifference erode that. Go out, enjoy yourself, and stop chasing after his approval and affection, live your best life without trying to include him in it, he will either carry on as he is or he will see that you are happy, but it's important not to place your happiness in other people's hands too much. x