It’s an error to conclude that every bad thing that happens to us is a demonic attack, just as it is to deny his existence and influence
I have a few “random thoughts” on these matters, largely drawn from my own experience. I’m no spiritual expert, but I’ve learned a few things along the way.
1) In my own journey with God, along with my wife Judy’s, as we go through life together, we have often noted how bad things often start happening when we are setting out to do something that is clearly in God's will. It's almost a running joke with us: “oh, that old devil is after us again, huh?, because we decided to [do so-and-so].” We pretty much laugh it off, mock the devil, and proceed on our path, exactly as we had intended.
We've come to recognize the banality and utter predictability of his attacks. In that sense, there is wisdom, I think, in a sort of mocking of the devil and a ho-hum attitude about it (the exact opposite of what the devil desires). It is completely to be expected and therefore a big yawn.
The fact that his opposition antics have no effect whatever on our plans, and that we are not daunted and reduced to abject fear by his attacks, no doubt drives the devil nuts. And that is more than reason enough to approach him in that way. It’s an application of “resist the devil and he will flee from you” (Jas 4:7; RSV).
2) C. S. Lewis knew quite a bit about the devil's designs, as exhibited in his masterpiece, The Screwtape Letters. In the same year he wrote that work (1942) he also wrote A Preface to Paradise Lost (on Milton's 17th century epic poem on the devil). Here is an excerpt:
What we see in Satan is the horrible co-existence of a subtle and incessant intellectual activity with an incapacity to understand anything. This doom he has brought upon himself; in order to avoid seeing one thing he has, almost voluntarily, incapacitated himself from seeing at all . . . He says 'Evil be thou my good' (which includes 'Nonsense be thou my sense') and his prayer is granted. (London: Oxford University Press, 99)
The devil is a cosmic fool and failure. We don't need to go along on his pathetic ride to hell. We already have the victory against him, and we need to be aware of that and confident that it is already in effect.
3) When undergoing suffering, my wife and I have always obtained great comfort by reading scriptural passages about suffering. It “works” every time. No exceptions! By understanding that suffering and pain are completely to be expected in the Christian life, we can defeat the devil's purpose of trying to take away our joy and peace.
4) Moreover, the Catholic understanding of redemptive suffering is a very beautiful thing. All suffering can be put to good spiritual purpose for the sake of souls and spiritual growth, and actually bring about joy.
5) When we become acquainted with Scripture and also the experience of the saints, we understand that very often we are greatly misunderstood and opposed, and have to suffer a great deal, when we faithfully follow the vocation that God gave us. Everyone – not just priests and religious – has a vocation (1 Cor 7:17).
If we’re sure (with prayer, self-examination, and counsel) that what we’re doing is in God's will, we won't be swayed by fallible and erroneous human criticism that comes our way for many different reasons, and is used mightily by the devil to cause self-doubt and self-condemnation. We must resolve ourselves to carry on, no matter what opposition we get, or where it comes from.
6) Most Catholics are aware of the great suffering that the saints go through, often including the “dark night of the soul.” The more we desire to follow God, the more we will be attacked: by both human beings and demonic forces. The Lord mightily uses those who understand this and who are willing to voluntarily undergo more suffering in order to grow spiritually and therefore aid other souls.
7) Human beings have different temperaments and personalities. Some of us are very insecure for various reasons. Some have a lot harder time accepting themselves and their failures than others. We have differing levels of self-confidence or self-image.
Some have had very troubled childhoods (or marriages, or personal losses, etc.) and have experienced suffering that the rest of us can only dimly imagine. According to the pain we have experienced, we are that much more weak, on a human level. The devil can exploit that, for sure, and use it to his nefarious ends.
Some of what we might think is “demonic oppression” may simply be a mood swing or a purely biochemical phenomenon. Life has its highs and lows, and illness affects this as well. We observe mood swings even in great biblical figures like the prophet Elijah. So we need to take into account whether something is purely a natural phenomenon rather than a supernatural, involving a direct attack from Satan himself.
In either case, we need to seek God's help in overcoming: through prayer, counsel, Bible-reading, fellowship, solace and support from friends and loved ones, medication (as the case may be), the sacraments, the Mass, adoration and other devotional practices, etc.
Our own internal psychological problems sometimes are falsely identified as “demonic attacks.” I'm not dismissing the reality of those attacks at all; I’m merely noting that some may be misinterpreted or ill-defined. Likewise, the Church does not regard all alleged Marian apparitions as authentic, without in the slightest denying the authentic ones.
It’s an error to conclude that every bad thing that happens to us is a demonic attack, just as it is to ignore the devil entirely, not to be vigilant against him, or to deny his existence. The devil can easily (and will!) exploit both extremes. The Catholic life is always one of balance between the extremes we so often see in the secular society and in our own lives.