Even not seeing them doesn't work, you just get daydreamy and gooey thinking about him. Loads of things, a town, a perfume, a song, a fleck of wool the glimpse of a red car; some little thing will remind you of him, and off you go.
Best thing is to give in and have a whirlwind. You and him against the world. Do things together, laugh, dance, enter combined experiences about which you can later reminisce. Enjoy love as a positive, uplifting, and rewarding experience.
You both know that you will return to America after Xmas, and that will be hard, but you will return wiser and more complete than if you deny yourself one of life's most glorious experiences and allow unrequited love gnaw you hollow.
Believe me, I've been there. A cute quotation serves here, "Love is nought but Grief wearing its Sunday clothes".