It will be a personal journey to you and you will definitely experience it and feel it, in a way which is familiar to you. My own experience gels with the words and experience of the Seers, in so far as I feel it as the experience of an inner state. It is an inner thrill; a tiny flame which grows with inner experiences and manifests itself in terms of Joy; Poise; Equilibrium; Love ... a glowing and radiant face ...
There may be outer problems or setbacks, but for one who knows how to look, it can easily be seen in the eyes, the seat of the Soul. Happiness has varying degrees and will decrease or increase according to outer circumstances. One may feel elated with a marriage or the birth of a child or sad and depressed because of bereavement, illness, loss of partnership and so forth. These are the transient or temporary forms.
Actually, it can also prepare one for the higher stages of happiness, where noisy things may happen on the outside, but the inner being remains peaceful. One arrives at that state due to intense prayer, selflessness and the love of mankind, which in themselves require an inner energy which comes from within; which some call Grace.
For this, receptivity is needed and receptivity requires a broad and open Heart; an expansive, not narrow life or selfishness; Gratitude to Something Higher and a constant daily practice of virtuous acts, assisting growth in this evolutionary cycle. Happiness cannot be found outside of the Will of the cosmic plan.
Finally, happiness is everyone's birthright. We are all flames of the divine, in isolation and trying to find our way home. The nearer we are to this Haven, the more our contentment increases. Much Love.