- It's medical. Check with your doctor to see if the reason for your lethargy is medically related. Perhaps you're depressed or low on iron — there are plenty of medical conditions that can cause you to be too tired to be motivated, so try to figure out if a medical condition is the cause of it.
- You're comfortable. If your life is quite comfortable, you may lose motivation to push yourself to grow. Keep in mind that it's always good to get out of your comfort zone, because that's the only way you can improve yourself. Do something you're hesitant about every week, and you'll find yourself getting used to it or even looking forward to the challenge after some time. It can be something small like asking someone you just met out for lunch, or a bigger move like giving honest feedback to your boss.
- Taking on too much. If you set unrealistic expectations, you are setting yourself up for higher chances of failing, which can cause you to lose motivation. Make sure your goals are actually achievable before setting them.
- You've given up. After so many failures, you may be immune to tackling challenges. It can be scary to put yourself out there again, but the greater the risk, the greater the rewards! If you're extremely gun-shy, take baby steps so you'll feel more confident once you manage to score small achievements.
- People around you. Maybe you have someone in your life who brings you down, perhaps out of their own insecurities or maybe because they can't adjust to the idea of a different you. Try to explain your reasons for attempting a change to them and ask for their support. If they can't come to terms with it, perhaps it's better to keep your distance until they come around.
Remember, the first step to overcoming obstacles is to figure out what's blocking you. Once you come to a better understanding, it'll be easier to get going and find your motivation again.