So, why should you aim to stay in a high vibration?
For the obvious; its just LOTS more fun!
Being in the vibes of bliss, happiness, peacefulness, joy is an amazing feeling ( why would you ever consciously choose to go out of it? )
From an energetic perspective, being in a high vibe state also allows the universe to help you more.
You get back what you sent out ( Law of Attraction ), so sending out high vibes is actually you asking to get the same high-vibe-experiences back.
Win win!
You are happy before, and the good things are able to come to you more, which can help you maintain your high frequency even more.