I am a big enemy of wishful thinking. Wishful thinking gets women (and presumably men) into a lot of trouble. One particularly dangerous form of wishful thinking is believing that the man with whom you are infatuated is an angel, a saint or just as decent a human being as you are when there is just no evidence of the above. All around you are hinting madly that Rufus is to be avoided, but you block them out. Rufus is attractive and therefore Rufus must be good. And, dear me, the painful explosion in the pit of your stomach the day you learn the hard way what a snake Rufus really is.
"Oh no," you think as panic swirls around your stomach and threatens to travel north. "Oh no, it can't be. It can't be true. He can't be doing this! Not after all [I've done/we've been through/his promises/I've suffered already].
But it CAN be true and Rufus CAN be doing it because feelings are not facts, and reality is what is and not what you want it to be.
If Rufus proves himself to be a snake, it is best to escape Rufus, for if you do not, Rufus will probably bite you again and again and, although you do not like it, you will get so used to being bitten that, should Rufus slither away from you, you will instinctively look for another snake, because snake-behaviour will seem normal and comfortable.
(By the way, never take particularly seriously an abused or used woman's opinion of what normal is. Many of my readers are made miserable by sexually-active-yet-unmarried college women telling you that your lives of quiet piety and chaste friendships aren't normal. Don't believe them. You are perfectly normal and a lot more in keeping with the past two thousand years of the history of, at very least, women who weren't prostitutes of one kind or another.*)
Once upon a time, after a breakup, I sat down with a pen and paper in a cafe and listed every man with whom I had gone on at least two dates, what they were like, whether I had courted them or if they had courted me, and why and how we broke up.
This was a very instructive exercise. It was akin to an exercise I did after a particularly horrible break-up with an alcoholic. Because women who date one alcoholic tend to go on to date other alcoholics, I thought very hard about who in my past life abused alcohol. And I remembered that one hard-drinking flame back in my undergrad days had told me that sometimes the only way he could get to sleep was to drink whisky until he passed out. And because of this and other memories I at 29 concluded what I at 21 had no way of knowing, which was that this flame was an alcoholic.
Sure enough, a mutual friend called me up a year or two after this exercise and sat, "I hope you're sitting down. [Ex-flame] has announced that he is...."
"Well, I know you're sensitive about this right now, but he says he's an alcoholic."
"Oh," I said, vastly relieved. "I knew that."
Anyway the point to this story is how helpful it can be to clearly grasp the patterns of your life, particularly your social life, by sitting down in a cafe with a pen and a paper and the whole afternoon before you.
But this is just a start. What you need to do, if you have not done so already, is develop a tough kind of mindfulness than hangs on to unpleasant facts about people rather than flinch away from them. This does not mean getting anxious about them. It does not mean becoming bitterly cynical. It just means being in possession of the facts.
For example, I have a friend who tells random fibs. The fibs are lazy and irrational; there is no reason for them as far as I can see. I wish my friend did not tell fibs, but she/he does.
Thinking about these lazy, silly fibs, I ponder my own relationships with the truth and whether I am word-perfect in my own representations of reality, or if there is room for improvement. In short, I look for the beam in my own eye, having observed the mote in my friend's. However, I do not forget my friend's fibs in the process, and although I am very fond of my friend, and he/she has many excellent qualities that make me glad he/she is my friend, I do not place more reliance on him/her than I think wise.
And to get through all this verbiage to get what I really want to say, If he let you down terribly once, and he has let you down terribly again and again since, what on earth makes you think he won't let you down terribly, or in an even worse way, later? Because the chances are that he will, and that you are setting yourself up for even more misery. Please put aside your hopes for a second to look history in the face. A leopard does not change his spots.
*One of the worst-paid kind of nineteenth-century prostitutes weren't "really" prostitutes but laundresses or servants who slept with university students for little presents or tips. But of course poor women tried to avoid such things unless they were desperate because, of course, they might get pregnant or some horrible disease [or lose their reputation, lose a quiet conscience, lose their self-respect, offend God, etc.]
Update: I see that it is the Feast of the Assumption. Dear me, what a thing to write about on the Feast of the Assumption. Better go to an appropriately pious blog for true edification this holy day. By the way, it is a Holy Day of Obligation in Scotland, so to Mass with you Catholic Scots and everyone else had better check to see if it is a HD of O in your area.