The happiness which brings enduring worth to life is not the superficial happiness that is dependent on circumstances. It is the happiness and contentment that fills the soul even in the midst of the most distressing circumstances and the most bitter environment. It is the kind of happiness that grins when things go wrong and smiles through the tears. The happiness for which our souls ache is one undisturbed by success or failure, one which will root deeply inside us and give inward relaxation, peace, and contentment, no matter what the surface problems may be. That kind of happiness stands in need of no outward stimulus. Billy Graham

The mind is its own place and in itself can make a heaven of hell; a hell of heaven. John Milton

Philippians 4:8
Summing it all up, friends, I'd say you'll do best by filling your minds and meditating on things true, noble, reputable, authentic, compelling, gracious—the best, not the worst; the beautiful, not the ugly; things to praise, not things to curse. Put into practice what you learned from me, what you heard and saw and realized. Do that, and God, who makes everything work together, will work you into his most excellent harmonies.