I messed up my diet today...?

You have to allow yourself to splurge a little every once in a while. If you never treat yourself, you will give up and it will hurt you more in the long run. Also never skip a meal, you should be eating 6 small meals a day, and do not eat anything 4 hours before sleep. Also it is best work out about 10-15 minutes as soon as you get up in the morning, and then eat breakfast. Also try to mix your meals up as often as possible.