I would try this 2-step plan:
1. Set up a meal plan
2. Follow it
When I'm dieting I'm following the plan day in, day out. There are no options. Randomly choosing foods and not following a proper plan only makes the diet prolonged. Personally, I would much rather spend that extra time gaining mass instead of trying to lose fat.
Yeah, I'm not too keen on IIFYM
But to answer your question: one day of being short of protein will not turn you into a skeleton, but if you have, say 100 calories left and you would need 50 grams of protein, personally, I would just eat it from low-fat cottage cheese (preferably one that tastes horrible so it doesn't happen again). And yes, I would eat as much as I needed to get that 50 grams of protein. (Yes, it will put you over the calorie goal, but such is life)