When a person’s faith is in himself, he would believe whatever he thinks or feels to be true and would not care to listen nor seek the truth. When a person’s faith is in man, he would easily believe whoever is that man that seems close to him or perhaps that man has a strong personality and is attractive so that he would believe what he says. But if a person’s faith is in God, he would seek the truth and not rely on his feelings. Feelings can be very deceitful. Our beliefs can affect our attitude, character, even our future. Our faith should be based on the truth not on man’s lies or our deceitful hearts. 

Thus saith the LORD; Cursed be the man that trusteth in man, and maketh flesh his arm, and whose heart departeth from the LORD. For he shall be like the heath in the desert, and shall not see when good cometh; but shall inhabit the parched places in the wilderness, in a salt land and not inhabited. Blessed is the man that trusteth in the LORD, and whose hope the LORD is. For he shall be as a tree planted by the waters, and that spreadeth out her roots by the river, and shall not see when heat cometh, but her leaf shall be green; and shall not be careful in the year of drought, neither shall cease from yielding fruit. The heart is deceitful above all things, and desperately wicked: who can know it?
(Jeremiah 17:5-9)

God forbid: yea, let God be true, but every man a liar; as it is written, That thou mightest be justified in thy sayings, and mightest overcome when thou art judged.
(Romans 3:4)

It is better to trust in the LORD than to put confidence in man.
(Psalms 118:8)

Prove all things; hold fast that which is good.
(1 Thessalonians 5:21)

Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
(John 5:39)

I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service. And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God. For I say, through the grace given unto me, to every man that is among you, not to think of himself more highly than he ought to think; but to think soberly, according as God hath dealt to every man the measure of faith.
(Romans 12:1-3)

He that is first in his own cause seemeth just; but his neighbour cometh and searcheth him.
(Proverbs 18:17)

Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.
(Isaiah 1:18)

Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God. Which things also we speak, not in the words which man’s wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual. But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned. But he that is spiritual judgeth all things, yet he himself is judged of no man.
(1 Corinthians 2:12-15)