Obviously you care about him, and want to celebrate him. But you're exhausted, plus feeling insecure. Its perfectly reasonable to say things didn't turn out like you planned, and can you meet tomorrow. Friends are flexible and don't give up on each other over one day or one visit. But, I guess everyone does friendship differently? If he can't meet tomorrow, express what you did in this post...how proud you are of him, and impressed, and that you'd love to learn a thing or two from him, since you are now facing your own challenges. You'd love to be there with him tonight, but you overextended yourself, and you're not able to tonight, but you're there in spirit.