<human>: Can you succinctly summarize the text in 1-3 sentences?

Back when I was in the Marine Corps, I had this girlfriend.  It turns out she was cheating on me the 2 years we were together (1 of them separated by my being posted in Japan).  It was pointed out to me multiple times by other Marines.  Once, someone I knew contacted me from the U.S. while I was in Japan to tell me a buddy of his met her at the mall, and she picked up on him.  Supposedly the buddy wasn't going to go out with her, since she was "a Marine's girl", but seeing all the cheating I saw in the Corps, I doubt that part is true, either.  Anyway, that's not the worst for me.  The worst 2 instances I can remember are:

1)  Finding a condom wrapper in her room that wasn't the brand I bought, and buying her line of B.S. that she didn't know where it came from.

2)  Dropping her off at a party at her ex-boyfriend's house.  She insisted they were just friends, and I had to get up extremely early the next day for surgery on a blown knee.  There was no one else at the house.  All lights except the living room light were out, no cars, etc.  I bought her line that we were just 15 minutes early, and left.

Now, I look back at the many signs she was cheating on me, and the stupid lines I bought and wonder "Who the hell buys a line of crap like that?!?" then basic honesty compels me to answer "Well, you did…idiot."

What about you, Reddit?  What is the stupidest thing you've ever accepted for a boyfriend/girlfriend?
<bot>: I bought obvious lies from a girlfriend that was cheating on me for 2 years, just for my own piece of mind.