How can Spiritual Practice bestow happiness to a man and why should someone peruse spiritual path? What if perusing Spiritual path yields more unhappiness to a person?
Man always strives for happiness. The pursuit of happiness is fundamental to this the six darshanas. The whole point of learning about Dharma from the karma kanda is to achieve Aihikam and Amushmikam, happiness in this life and heaven, respectively. But learning about Brahman from the Vedanta is very different – it is to achieve Nihshreyasam, the bliss of moksha (liberation).
Talks with Ramana Maharshi, Talk 28
D.: What is happiness? Is it inhering in the Atman or in the object, or in the contact between the subject and the object? But we do not see happiness in our affairs. When does It actually arise?
M.: When there is contact of a desirable sort or memory thereof, and when there is freedom from undesirable contacts or memory thereof, we say there is happiness. Such happiness is relative and is better called pleasure.
But men want absolute and permanent happiness. This does not reside in objects, but in the Absolute. It is Peace free from pain and pleasure.
D.: In what sense is happiness our real nature?
M.: Perfect Bliss is Brahman. Perfect Peace is of the Self. That alone exists and is conscious. The same conclusion is arrived at: (a) judged metaphysically, and (b) inferred by Bhakti Marga (Path of Devotion)
Pleasure and pain are relative and refer to our finite state, with progress by satisfaction of want. If relative progress is stopped and the soul merges into Brahman - of the nature of perfect peace - that soul ceases to have relative, temporary pleasure and enjoys perfect peace - Bliss. Hence Self Realisation is Bliss; it is realizing the Self as the limitless spiritual eye (jnana dristi) and not clairvoyance; it is the highest self surrender. Samsara (the world-cycle) is sorrow
This bliss is something that does not fade with time. To understand and ultimately free ourselves from all suffering, we must therefore develop minds that are impervious to the transitory nature of the outside world. To understand this, we need to recognize what is ephemeral versus what is eternal and cultivate the dispassion necessary to be able to reject that which is ephemeral, in our pursuit of the eternal. This means that if our goal is to live a truly happy life, we must stop seeking happiness in what is transitory.
What is worth seeking and discovering is the truth of Self. Such knowledge comes only to the still, clear intellect not muddled by strenuous search [outside] but questing for the Truth [inside] in silence.
The point of spiritual practice is not to maximize your material assets and minimize your losses, but to be free of attachment to either gain or loss and to be peaceful and blissful amidst the vicissitudes of life.
That 'how' question is complicated to tackle in this case, as it tries to ask that mecanism underneath. One has to experience that happiness through the means of practice.
Quoting from the Foreword of Sarvollāsatantram written by M.M.Gopinath Kaviraj
Ānanda is the expression of the eternally self aware Supreme-Being acting upon itself and looking into itself as into a mirror.
Can one really translate that Ānanada into happiness which has that sadness as an Antonym?
From Nila-Saraswati tantra,
परमानन्देन संयुक्तो मुक्तियास्यति निश्चिता । इति सत्य पुनः सत्यं सत्यं वच्मि वरानने ॥
O Vararane, 'Mukti' is achived only after attaining that ParamAnanda, This is truth! This is Truth! This is the only Truth!
Tantras recognize that the ParamAnanad is achived through that transmutation of Jīva into Shivā, often pictured as the Awakening of Kundalini and its unification into the Sahashara-Chakra. Essentially this falls down to the Knowledge. (I tried emphasizing that here) Unless knowledge rises one cannot achive that Ānanada. The spiritual path is the only way for it,
अध्यात्मविद्या हि नृणां सौख्यमोक्षकरी भवेत । धर्मकर्म तथा जप्यमेतत् सर्व निवर्तते ॥६॥।
Only the adhyātma Vidyā can bring happiness and Moksha to the Humans. There is no other equivalent Vidyā to it. All Dhrmha-Karma, japa-tapas dissolution happens in this Vidyā.
What if the spiritual path yields more unhappiness? Spiritual path can yield unhappiness if not performed correctly. (That Oghavigna can become a cause too) Also the ways of spirituality change in each yuga,
From the Kaankal-Malini tantra,
सत्यत्रेतायूगं देवि द्वापारं सुखसाधनम । कलिकाले दुराधर्ष सर्वदुःखमयं सदा ॥१४॥
In Satya, Dwapar & Treta Yuga the Sadhanas performed for the purpose of happiness attained completion. The same Sadhanas in Kali-Kal give Sadness and bring suffering.
This lines are taken from 'PuraCharan vidhi' (पूरश्चरण). Due to that 'Sadness', Tantras prescribe japa, infact often mention that japa is the only means.
Given the horrible nature of Samsara people believe that spirituality enables a person to escape the horrors of the world.
Ocean of Life – Need for Moksha
"That Ocean, so terrible has sorrow for its waters. Anxiety and grief constitute its deep lakes. Disease and Death are its gigantic alligators. The great fears that strike the heart at every step are its huge snakes. The deeds inspired by Tamas are its tortoises. Those inspired by Rajas are its fishes. Wisdom constitutes the raft for crossing it. The affections entertained for objects of the senses are its mire. Decrepitude constitutes its region of grief and trouble. Knowledge..is its island. Acts constitute its great depth. Truth is its shores. Pious observances constitute the verdant weeds floating on its bosom. Envy constitutes its rapid and mighty current. The diverse sentiments of the heart constitute its mines. The diverse kinds of gratification are its valuable gems. Grief and fever are its winds. Misery and thirst are its mighty eddies. Painful and fatal diseases are its huge elephants. The assemblages of bones are its flight of steps and phlegm is its froth. Gifts are its pearl-banks. The lakes of blood are its corals. Loud laughter constitutes its roars. Diverse sciences are its impassibility. Tears are its brine. Renunciation of company constitutes the high refuge (of those that seek to cross it). Children and spouses are its unnumbered leeches. Friends and kinsmen are the cities and towns on its shores. Abstention from injury and Truth are its boundary line. Death is its storm-wave. The knowledge of Vedanta is its island (capable of affording refuge to those that are tossed upon its waters). Acts of compassion towards all creatures constitute its life-buoys, and Emancipation is the priceless commodity offered to those voyaging on the waters in search of merchandise. "
Mahabharata Santi Parva Section CCCIII
What if this path does not give us happiness. Then you can always resume sinful life and come back to the horrors of Samsara.