Surya Namaskar and giving arghya are different. You are talking about arghya i.e., offering handful of water.
It is generally believed that Sun likes offering of water through arghya. This offering is called arghya pradanam which is part of Suryopasana which is also a part of Sandhyavandanam ritual. People also offer arghya to the Sun god exclusive of Sandhyavandanam ritual also. There are group of rakshasas called Mandehas who fight with Sun god and obstruct his path. The water we offer will help him and clears the way. Hence, you are helping Sun god.
Lord Surya bestows good health. Matsya Purana contains following verse
ārogyaṃ bhāskarādiccheddhanamiccheddhutāśanāt /
īśvarājjñānam anvicchenmokṣam icchejjanārdanāt // (41)
Health ought to be sought from the Sun, wealth from Agni, knowledge from Isvara, and emancipation from Janardana.
And a similar verse which gives the same meaning from Padma Purana
O lord of kings, he would fulfil all his desires with little effort. One should seek knowledge from Sankara, and (good) health from Bhaskara (i.e. the Sun). One should desire wealth from Hutasana (i.e. Fire), and position from Janardana (i.e. Visnu). One should seek Vedic (i.e. sacred knowledge), giving peace to all beings, from the grandsire.
So, you will be bestowed with good health in near future and blessed with long life. There is worship of sun in many scriptures like Puranas and Itihasas. Lord Rama got victory after worshipping Sun god through Aditya Hridayam. According to Saura Puranas like Samba Purana, Sun god is manifestation of Brahman or Brahman himself. He is called Pratyakshya Bhagavan meaning the God we see daily who nourishes the life on the earth. So, you will be benefited in many ways besides health too.
Do not stop worshipping God and keep up the faith. Be patient. The fruits will be awards gradually. It is not a waste of time.