peace!
Feelings about God varies at different stages of spiritual development.
1= In the beginning of Holy Quran it is said:
This is a perfect Book; there is no doubt in it; (it is) a guidance for the righteous, Who believe in the unseen and observe Prayer, and spend out of what We have provided for them; And who believe in that which has been revealed to thee, and that which was revealed before thee, and they have firm faith in what is (yet) to come.It is they who follow the guidance of their Lord and it is they who sahll prosper. [chapter2, verses 3 to 6]
Hence, at the start of spiritual journey idea of believe in UNSEEN is mentioned which includes God .
2= Then remembrance of God, doing good acts and following the instructions revealed in the Book lift person's feeling about God.
For example, just after the verses about the benefits of holy month of fasting (Ramadan), God says:
And when My servants ask thee about Me, (say) I am near . I answer the prayer of the supplicant when he prays to Me. So they should hearken to Me and believe in Me, that they may follow the right way. [ 2:187]
So going throught he spiritual exercises of fasting month ( which is comprised of fasting plus lots of remembering of God ), progress about feelings of God grows from "UNSEEN" TO "I AM NEAR".
3= The feelings of The blessed holy Prophet about God illumine the subject:
Say, My Prayer and my sacrifice and my life and my death are (all) for Allah. the Lord of the worlds. [6:163]
And
Verily, those who swear allegiance to thee indeed swear allegiance to Allah. The hand of Allah is over their hands. So whoever breaks (his oath), breaks (it) to his own loss; and whoever fulfils the covenant that he has made with Allah, He will surely give him a great reward.[48:11]
4= When one spiritually grows with Holy Quran, it makes the spiritual journey of a person from believe in UNSEEN to :
Say, He is Allah, the One; Allah, the Independent and Besought of all. He begets not, nor is He begotton; and there is none like unto Him. [ 3rd last chapter # 112 : verses 2 to 5]
5= All along the Quran various attributes of God are mentioned :
Allah -- there is no God but He, The Living, the self Subsisting and All-Sustaining. Slumber seizes Him not, nor sleep. To Him belongs whatsoever is in the heavens and whatsoever is in the earth. Who is he that will intercede with Him except by His permission? He knows what is before them and what is behind them; and they encompasss nothing of His knowledge except what He pleases. His knowledge extends over the heavens and the earth; and the care of them burdens Him not; and he is The High, the Great . [2:256]
6= Hence the effect upon one's heart and mind is feeling of His great Presence and the spiritual light seen through inner eyes.