Praying to Sun god (Suryopasana) has many benefits described in Vedas. According to Rig Veda, Book 1, Hymn 50,
Surya is the remover of heart disease and yellowness of body.
उद्यन्नद्य मित्रमह आरोहन्नुत्तरां दिवम |
हर्द्रोगं ममसूर्य हरिमाणं च नाशय ||
11 Rising this day, O rich in friends, ascending to the loftier heaven,
Sūrya remove my heart's disease, take from me this my yellow hue.
Also praying to
Surya can give us strength and can remove various diseases as described in Rig Veda, Book 10, Hymn 37.
येन सूर्य जयोतिषा बाधसे तमो जगच्च विश्वमुदियर्षिभानुना |
तेनास्मद विश्वामनिरामनाहुतिमपामीवामप दुष्वप्न्यं सुव ||
4 O Sūrya, with the light whereby thou scatterest gloom, and with thy ray impellest every moving thing,
Keep far from us all feeble, worthless sacrifice, and drive away disease and every evil dream.
Surya is the provider of happiness and maximum age.
तं नो दयावाप्र्थिवी तन न आप इन्द्रः शर्ण्वन्तु मरुतोहवं वचः |
मा शूने भूम सूर्यस्य सन्द्र्शिभद्रं जीवन्तो जरणामशीमहि ||
6 This invocation, these our words may Heaven and Earth, and Indra and the Waters and the Maruts hear.
Ne’er may we suffer want in presence of the Sun, and, living happy lives, may we attain old age.
विश्वाहा तवा सुमनसः सुचक्षसः परजावन्तो अनमीवानागसः |
उद्यन्तं तवा मित्रमहो दिवे-दिवे जयोग जीवाःप्रति पश्येम सूर्य ||
7 Cheerful in spirit, evermore, and keen of sight, with store of children, free from sickness and from sin,
Long-living, may we look, O Sūrya, upon thee uprising day by day, thou great as Mitra is!
महि जयोतिर्बिभ्रतं तवा विचक्षण भास्वन्तं चक्षुषे चक्षुषे मयः |
आरोहन्तं बर्हतः पाजसस परि वयंजीवाः परति पश्येम सूर्य ||
8 Sūrya, may we live long and look upon thee still, thee, O Far-seeing One, bringing the glorious light,
The radiant God, the spring of joy to every eye, as thou art mounting up o’er the high shining flood.
Surya is also capable of giving pure innocence, strength, and health.
यस्य ते विश्वा भुवनानि केतुना पर चेरते नि च विशन्तेक्तुभिः |
अनागास्त्वेन हरिकेश सूर्याह्नाह्ना नोवस्यसा-वस्यसोदिहि ||
9 Thou by whose lustre all the world of life comes forth, and by thy beams again returns unto its rest,
O Sūrya with the golden hair, ascend for us day after day, still bringing purer innocence.
शं नो भव चक्षसा शं नो अह्ना शं भानुना शंहिमा शं घर्णेन |
यथा शमध्वञ्छमसद दुरोणेतत सूर्य दरविणं धेहि चित्रम ||
10 Bless us with shine, bless us with perfect daylight, bless us with cold, with fervent heat and lustre.
Bestow on us, O Sūrya, varied riches, to bless us in our home and when we travel.
अस्माकं देवा उभयाय जन्मने शर्म यछत दविपदेचतुष्पदे |
अदत पिबदूर्जयमानमाशितं तदस्मेशं योररपो दधातन ||
11 Gods, to our living creatures of both kinds vouchsafe protection, both to bipeds and to quadrupeds,
That they may drink and eat invigorating food. So grant us health and strength and perfect innocence.
As suggested by @Tezz, According to Yajur Veda 4.5.1
Surya is the form of
Rudra. So, he is the provider of happiness to everyone.
असौ योsवसर्पति नीलग्रीवो विलोहितः ।
उतैनं गोपा अदृशन्नदृशन्नुदहार्यः ॥
उतैनं विश्वा भूतानि स दृष्टो मृडयाति नः ॥
The black-throated Rudra who has assumed the form of the sun that glows red when rising. Him the cowherds, the women carrying water, and all the creatures behold. He, who is seen by all, let Him send happiness to us.