One of the best workouts that I love/hate to do is interval training. Interval training is a great way burn extra calories in your workout compared to steady state cardio training. Basically think of your body firing up the way your car does when you first start to accelerate. You and your car both burn through extra fuel until you get to a steady speed or state. So extra calories burned for you (and extra gas for your car).
If you push yourself effort wise for a period of time and then drop to a slower speed or reduced effort and repeat that whole process again, you use a lot of extra calories to power your body. In addition, you work to improving your VO2 max improving your overall running speed. From a mental perspective, when you push yourself physically to a level of discomfort and know that you are going to be able to recover from it, you build more confidence into your running.
You can do interval training running outside or in or biking or rowing. All you need is a watch and a relatively flat surface.
Start by warming up throughly, for at least 10 minutes.
Then choose your interval time. Typically 1 minute at 90-95% of my maximum effort followed with 1 minute of rest.
Repeat 5-6 times.
Followed up with a10 minute cool down.
This is an intense workout but again really effective for boosting metabolic and mental performance related to running or any other endurance sport.