Im on a diet and feel guity i eat so much?

this morning my co workers had a bbq at work and they made carne asada, which is some type of beef . i had 3 pieces of beef with tortilla. now i feel very guilty is only 1pm. im on a very strict diet iv been doing good until now i have lost 12lb. how can i make it up? i was thinking of lifting weights than going for a 3 mile run and just eat fruits and a cup of tomato soup from subway for the rest of the day . what you guys think?