First try not to get too stressed out or overly critical of the situation, stress can lead to increased weight and if you "beat yourself up" figuratively speaking, you may feel too depressed or helpless the engage in the activities required to get back on track.
Take a little bit and make a list of the foods and drinks you normally consume throughout the day, as far back as you can remember, and look for things you should be eliminating or swapping out for healthier options. For example, if you are drinking more pop, sugary juices, or energy drinks than you may have realized try switching them out for some ice cold water. If you notice that you are snacking on "junk food" try swapping the junk food out for some fruit like bananas, apples, or grapes. If your meals are very sporatic, spread out over long periods of time (8-10 hours+) or your portions are more than you need try shooting for SMALL portioned meals more frequently (some people suggest upwards of 6 meals a day if the portions are small enough). The reason for the small portions more often is it keeps your metabolism moving throughout the day and gives you more energy to stay active. If you go too long without eating you will go into starvation mode and if you eat a large meal while your body is in that mode it is going to hang on to whatever it can.
Other than that stay as active as you can throughout the day. When you go to the store park farther away so you have to walk more. Take the stairs rather than the elevator or escalator. If your not getting too much at the store use a hand basket rather than a shopping cart. In general avoid the easy way out when it comes to daily activities and these little changes may add up and help. You should also be staying physically active in general with exercise, 30 minutes a day of moderate physical activity is a great goal to shoot for.
