While searching for something else, I found an interesting passage in Augustine’s De Trinitate, book 12, chapter 12:
… when the mind is pleased in thought alone with unlawful things, while not indeed determining that they are to be done, but yet holding and pondering gladly things which ought to have been rejected the very moment they touched the mind, it cannot be denied to be a sin, but far less than if it were also determined to accomplished it in outward act.
And therefore pardon must be sought for such thoughts too, and the breast must be smitten, and it must be said, “Forgive us our debts;” and what follows must be done, and must be joined in our prayer, “As we also forgive our debtors.”
The sins of the mind and imagination seem particularly relevant to the internet. What do we allow to enter our minds?
Equally by chance, I saw on Facebook a quotation of Proverbs 4:23 from something called the New Century Version:
Be careful what you think,
because your thoughts run your life.
Which is a novel rendering of the usual text:
Above all else, guard your heart,
for everything you do flows from it.
I don’t think we should over-analyse ourselves. But I pass these thoughts on in case God is speaking to anyone through them.