Do you think a food diary is helpful?

i eat healthy all throughout the day, but then at night, right before bed, i cave and start eating too much sugar. i think what once was temporary emotional eating has turned into a bad habit that i perform nightly. so i'm thinking of keeping a food diary to keep in check at night when i start having those cravings for sugar. do you think a food diary will help me? i've also bought casein, which i want to start drinking before bed to keep me full at night.