Celebrity trainer David Kirsch is well-known for his work with A-list models and actresses such as Heidi Klum, Kate Upton, Liv Tyler, and Anne Hathaway.

In his latest book, "Ultimate Family Wellness," David shares his own story of balancing fatherhood with fitness, and gives his expert advice on how to work out and eat well with the whole family.

Here, David shares his suggestions for why your workout plan may not be working out for you, and how to get the most out of your fitness regime.

You don't have a proper plan

Workouts often start and fail in the planning (or lack thereof) stage. Before you take your first step, ask yourself the "what, why, and for whom" of your routine. What do you hope to accomplish? Why are you doing this, and for whom? Simply put, for a diet and exercise program to be successful, you need a specific goal (e.g., lose weight, tone up) and a clear course of action (i.e., the right program) to fit your lifestyle and budget.

Last but not least, make sure you are doing this for yourself and not someone else. Doing it for someone else will leave you feeling resentful and unfulfilled and ultimately sabotage and undermine the possibility of realizing your wellness goals. Once you've satisfactorily answered the "what, why, and for whom," set a realistic goal and timeline.

You aren't in the moment

In my book "Sound Mind, Sound Body," I advise readers to take time out of their days to "honor" themselves. Here, I make that same recommendation. This is the time of day you dedicate to your wellness. Make every moment of those five-minute exercise circuits count. When you physically leave the office, mentally leave the office behind. Turn off your cell phone. Workout time is not time to socialize, catch up on your soap operas or Google Chat with your friends. Too often I see people "walking through" their workouts, which can lead to injury, unrealized goals, and ultimately complete dissatisfaction with a training routine.

To make the most out of your workouts, stay focused, engage your brain, and visualize the body you were meant to have. Want it, will it, make it happen.

You don't get enough sleep

Failure to get adequate sleep will, among other things, leave you feeling depleted mentally and physically and will sabotage your hard-earned workout gains. It can elevate your cortisol levels, which can lead to weight gain. Lastly, poor eating habits and sleep deprivation usually go hand in hand. When you feel tired, you often make bad food choices (e.g., eat comfort foods because they're convenient rather than healthy foods).

You don't get proper fuel

I like to say "Eat to live." Starving your body will only serve to upend your fitness/wellness transformation. You need a balanced diet. Fill up on fruits, vegetables, grains, lean proteins, legumes, nuts, and seeds. Small, abundant healthful meals throughout the day will keep you optimally fueled and keep your brain, organs, and body working efficiently.