A lot of people may get into a fitness rut when they are not looking at exercise in the right light.
If you're feeling like you're in a fitness rut, try adjusting your attitude. Exercise can only take you so far mentally, which means you may need to take a step back and think realistically about what you are trying to get out of it. Not everyone can look like Jessica Biel. In fact only Jessica Biel can look like Jessica Biel so even if you do her exact plyometrics routine, you may not get the same results. Heck, I do plyometrics all the time but my bod looks nothing like hers. If your goals are unrealistic, you may become discouraged, which is completely counterproductive.
Accept who you are. Realize that your body has limits -- I invite you to push those limits because chances are you could be pleasantly surprised, but always stay realistic. Step one is accepting your body for what it is and appreciating what it is capable of doing, not putting it down for what it is not capable of doing.