I can't remember when I first heard this one, but I'm sure I must have been confused. In English, when we talk about "tension," it usually holds a more negative connotation (unless maybe you're talking about "sexual tension"). There's often a high degree of tension between two individuals who don't get along, for example, right?
In Japanese, "high tension" or 「ハイテンション」 has a positive meaning - to be excited or enthusiastic. I suppose this flows from the fact that when we talk about electricity, "high tension" means we're talking about a lot of energy.
An example from ALC:
(I strive to be bright and cheerful so as not to let my family worry.)