The several thousand year old practice of "Mindfulness". Derived from the earlier (pre-Buddhist) practice "Vipashyana" (i.e., clear seeing).

Yes, keeping one's mind centered, aka, in the present moment, in awareness, is being happy. Being happy without external causes.

Unhappiness is basically thought-forms or thought-waves saying "I am unhappy" or "I am bored" or "I will be happy when ...". There is no more reality to unhappiness than mere thought-forms. The underlying silence revealed by a still mind is happiness itself.