Calorie deficit

Ive been in a calorie deficit but have struggled to lose weight. For example today I went to the gym for an hour and only ate 250g of prawns and a packet of crisps/chips. I would normally eat more, but have just been feeling terrible in the deficit. Most of the time i would be having 1500 calories and burning around 450 in the gym. If anyone can help me with tips and things like that.