The quote might be something from a sermon and
'1 Peter' only a reference.

1 Pet. 5:8 (Douay-Rheims) reads
'Be sober and watch: because your adversary the devil,
as a roaring lion, goeth about seeking whom he may
devour.'.

Satan's principal sin is pride, is it not?
He hides only occasionally and often considers
himself a benefactor of men.

What men can watch out for and, indeed, have watched out
for is inconsistencies. Mark 3:26 :
'And if Satan be risen up against himself, he is divided,
and cannot stand, but hath an end.'.
An ability to spot inconsistencies early is likely to help.
Unfortunately, proofs are not part of many syllabi these
days. Not that only Satan runs into inconsistencies; men,
whatever their intentions, also do. And they also then
cannot stand and fall. So they might be persuaded to pick
up some logic even before considering God and Satan.

Sounds good, @Umbra Catti. But we cannot control all logic, I guess. I think sincerity and humility are most important. You recognize the bad by it's lies. I like this:

Satan’s principal sin is pride, is it not?

Not sure if I got you right. And English is not my native language.
I meant there can always be a mistake in thinking. It's good to bear that in mind: I could be wrong, forgot some crucial factor. And I meant like... I cannot argue with anyone. I cannot try to research every question in order to find inconsistencies. Time is important. I'm losing control if I try to fight everything I feel to be bad by mere logical thinking.

For me it's the other way round: First, rather simple step, is to think myself. It's what many people have forgotten, I guess. They just believe what they're told, and don't reflect on it. It seems so obvious how logically wrong and bad from the heart so much is that we can see in front of our eyes now. But actually it's not to difficult to look for some information and do some logical evaluation. I absolutely support what you demand. Knowledge can be powerful.

But second step is to believe. And that's more difficult, I think. It can mean to somehow love and understand the people I think are being caught by some bad ways. And sometimes it helps both sides to find something that feels like good.

You know, I'm not fighting people. I try to fight what evil is. And the evil hates love. Much more than logic.

I'm sorry, I guess it was to late for me to write this comment. Hope it still makes some sense. Will go to bed. Good night.

A very good Tuesday to you, @Christian Bredlow.

Kipling's "If" comes to mind:
'If you can trust yourself when all men doubt you,
But make allowance for their doubting too;'.
This is about one's fallibility.
One can miscalculate oneself or accept without checking
a miscalculation of another. It is more or less clear
what one can do to avoid the former error; the latter
is more difficult to avoid.
Yes, we have not the time to check everything.
But this is not to say that we should accept everything
that we do not check. If we have caught someone lying,
we should expect him to lie on subsequent occasions as
well. We should not accuse him -- without checking --
of lying on these subsequent occasions but neither should
we believe him.
Fighting is another matter; it is not often that we can
do something about the ills we observe.

Checking for inconsistency is probably the easiest
checking there is, and having discovered an inconsistency
we can often discard a big batch of "information" --
without bothering about the motives and abilities at its
source.

I may not understand your paragraph on believing.
Of course, most of human lying is unintentional,
and even intentional liars are not beyond redemption.

I do not think that evil always comes hand in hand with
hate. Think of the millions of soldiers who have sworn
to kill to order and done it. My own worst sins have not
been accompanied by hate.

Here are some vaguely relevant stories:
diasporing.ch/posts/9bd922c0cd… .