I have seen people actually undermine others' confidence on purpose. There seems to be an evil maliciousness in some people who do not like to see other people confident in God.
I think this evil may be envy of the good. Or, it may be the hatred of joy.
Hope gives us real confidence in God. St. Therese of the Child Jesus is one saint who points us to confidence, even in the middle of great suffering.
For those who think she did not suffer, read this.
"I get tired of the darkness all around me. The darkness itself seems to borrow, from the sinners who live in it, the gift of speech. I hear its mocking accents: It's all a dream, this talk of a heavenly country, of a God who made it all, who is to be your possession in eternity! All right, go on longing for death! But death will make nonsense of your hopes; it will only mean a night darker than ever, the night of mere non-existence!" (SS, Ms. C., Knox translation)
Even the Little Flower was tempted to doubt, assailed by the evil demons who surrounded her in her trials. But, she did not give in to doubt and overcame sins against hope, either despair or presumption.
Do not listen to those who undermine your faith, your hope, your love.
Look to Jesus.