“Whosoever believeth that Jesus is the Christ is born of God: and everyone that loveth Him that begot loveth him also that is begotten of Him.” –  1John 5:1

We have known many who, by hearing continually the most precious doctrine that belief in Jesus Christ is saving, have forgotten other truths, and have concluded that they were saved when they were not, have fancied they believed when as yet they were total strangers to the experience which always attends true faith. They have imagined faith to be the same thing as a presumptuous confidence of safety in Christ, not grounded upon the divine Word when rightly understood, nor proved by any facts in their own souls. Whenever self-examination has been proposed to them they have avoided it as an assault upon their assurance, and when they have been urged to try themselves by gospel tests, they have defended their false peace by the notion that to raise a question about their certain salvation would be unbelief. Thus, I fear, the conceit of supposed faith in Christ has placed them in an almost hopeless position, since the warnings and admonitions of the gospel have been set aside by their fatal persuasion that it is needless to attend to them, and only necessary to cling tenaciously to the belief that all has been done long ago for us by Christ Jesus, and that godly fear and careful walking are superfluities, if not actually an offence against the gospel.

On the other hand, we have known others who have received the doctrine of justification by faith as a part of their creed, and yet have not accepted it as a practical fact that the believer is saved. They so much feel that they must be renewed in the spirit of their minds, that they are always looking within themselves for evidences, and are the subjects of perpetual doubts… There is a tendency in some hearts to look too much within, and spend more time studying their outward evidences and their inward feelings, than in learning the fullness, freeness, and all sufficiency of the grace of God in Christ Jesus. They too much obscure the grand evangelical truth that the believer’s acceptance with God is not in himself, but in Christ Jesus, that we are cleansed through the blood of Jesus, that we are clothed in the righteousness of Jesus, and are, in a word, “accepted in the Beloved.” ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0979.cfm