Seeking God in meditation is the direct way to attain a joyous and youthful state of mind. There are additional practices that will also help to nurture mental youthfulness. First of all, learn to smile – sincere smiles. Wherever you are, no matter how trying the circumstances, smile from your heart. Harbor no form of anger or malice. Try to give genuine smiles to all – friends, family, strangers alike. Half the secret of youthfulness lies in that. If you have a contagious smile that wells up from your true inner being, you are youthful. I often say that if you can’t smile, then stand before a mirror and train yourself to smile by pulling the corners of your mouth up!
The day you make up your mind to smile, you will see that everything seems to conspire to try to make you cry! That is life. The day you make up your mind to be patient and forgiving, it will seem that others suddenly become harder to get along with. That is life. We are often crucified by others, but their meanness should not affect our resolutions to be kind. Let others pursue their way; you be bigger and adhere to your way. It is not the approval of human beings that you want, but the certification of God. Once you find His pleasure, you will be happy. Try to please others insofar as you can, and try not to offend anybody; but don’t let that work against your primary duty to please God, first and foremost.
Practice your smile of mental youthfulness all the time. See how many hours at a time you can keep your balance in spite of your trials. When you can remain cheerfully even minded always, you will find every cell of your body alive with great joy.
Paramahansa Yogananda, Journey To Self Realization