1. "Between my job, my family, and my friends, I don't have time to work out!"

    Real-World Advice: Exercise first thing in the morning
    Since there are usually fewer conflicts at 6 a.m. than there are at 6 p.m., morning exercisers tend to stick to their routines better than people who work out later in the day. To shift your workout times, gradually set your alarm to go off 15 or 20 minutes earlier until you're waking up an hour earlier. And try to get up at the same time ever day whether you're exercising or not.

  2. "When I can exercise, I'm too exhausted."

    Real-World Advice: Trick your body and your brain
    If you don't want to run, tell yourself you'll take just a short walk. When you've moving, more blood and oxygen are being pumped to your brain and muscles, so you feel better. After a few minutes, you'll probably feel energize and want to step up the pace or go longer.

  3. "I travel all the time, so it's difficult to stick to a routine."

    Real-World Advice: Take your workout on the road
    If you have a choice of hotels, book those with good gyms or near outdoor recreation areas. If you'll be stuck in your room, pack a lightweight resistance band or tube to do strength moves.

  4. "I'm self-conscious and going to the gym intimidates me."

    Real-World Advice: Find a supportive environment
    Women-only gyms are cropping up across the country, and many co-ed clubs are creating female-only workout areas. The best way to get used to the gym environment is to hire a personal trainer, who can walk you through moves and show you how to use the machines.

Pick up Shape's special Make Over Your Body issue for complete details about this 21-day plan. On newsstands now!