Cardiovascular exercise takes more energy than it gives at the beginning but your body will get less easily tired further down the road. So yes, activities can give energy.
Not sure why you're being downvoted because it seems true to me:
For example, starting out with running feels very exhaustive and draining but once you're in the habit of it you overall feel more energetic I believe.
This is true and was proven by numerous scientific observations. Mild physical and intellectual activities indeed improve cellular energy levels to some degree.
Nobody really knows how it works exactly, but it's a fact.
For example, starting out with running feels very exhaustive and draining but once you're in the habit of it you overall feel more energetic I believe.