To keep your mind smiling you need to keep exploring.
To keep your mind exploring you need to keep yourself physically well.
To keep yourself physically well you need a mind which highly values self care.
Self care = self esteem and and vice versa. This provides the self confidence required to ’explore’.  

Self Care for the Mind:
Read widely. Books (fiction & non), mags, journals, reports, comics, blogs. Read something everyday. 
Watch a variety of TV shows, docos, movies.
Talk to all sorts of wierd and wonderful people. Appreciate their differences.
Do a course, study something. Keep learning and providing your brain with new information to sort through. 
Take time out every week to reflect. Learn from your mistakes, be grateful for all you have and stay focused on what you’re working towards.
Take time out every week just to think. Explore your ideas and the ideas of others, it will enliven you.
Manage your worries by talking to your ’confidant’ – a stable friend/family member, counsellor, therapist. It’s often better to lean on an indepnadant mentor who is not involved in your life and therefore has no particular investment in any particular outcome.   
Be open to the diversity life offers and be mindful of the fact that it would be remarkably dull without it. 

Self care for the body. 
Make exercise a part of your day. It’s essential NOT optional.
Do a variety of exercises which keep your body strong and flexible as well as ones which keep your heart and lungs healthy.
Eat well everyday. Eat appropriately portioned nutritional foods MOST of the time.
Sleep. Don’t underestimate the importance of sleeping well, it restores and rejuvenates your entire being.
Hydrate. Drinks lots of water everyday. 
Touch. Enjoy a big warm hug or have a massage. Your mind will benefit immensely from it.

Explore and smile.
It’s a wonderful life we have here, you gotta love it warts and all!