I'm one of those optimistic and trusting people who have foolishly given out undeserving second and third chances.

From men to friends and even acquaintances, I've forgiven when others would have told them to shove it.

Naturally, I get angry and try my luck at holding a record-breaking grudge. But somehow, I always get over it sooner than my hubris wants me to.

I believe it's because I never really knew how to say goodbye without feeling uneasy — until recently.

An old and once-close friend and I have had a falling out; I am completely OK with that.

Our quarrel stemmed from a disagreement that was more than just a war of words. It was the conclusion to a series of shady events that became the absolute last straw for me.

I'm always willing to bury the hatchet, but there are some things my mind refuses to let me forget.

In describing my ex-friend, I'd say she's a woman driven by desire for unprecedented success, which I always admired. I'd also say she's further driven by the need to be loved, even at the expense of her happiness and friendships.

In recent months, we spoke and hung out regularly. Then, I suddenly stopped hearing much from her.

Our work schedules had become pretty hectic, so I didn't dwell on it at first. But I don't think it's a coincidence that she'd gotten herself into a new fling so, presumably, our friendship had to take a back seat.

I'm not surprised, though, because this is her usual conduct.

Let's backtrack to 2005 when I was dating a guy she introduced me to. I didn't like him much, but I was 14 and it was cool to say, "Yeah, I have a boyfriend. How about you?"

One day, she called to let me know that she'd regrettably made out with him while he and I were just starting our relationship.

It was never about the boy, but always about the principle.

After that, I stopped talking to her for a few years and during that time, she actually went on to date him. Obviously, she didn't co-write the friendship handbook.

Fast-forward to many years later, when we were much older and in college. She was once again my bestie and the story of "our" ex-boyfriend was something we'd now laugh about.

I visited her while she was away at school and met one of her college best friends. An all-too-familiar look of confusion bombarded my face when her friend approached me, saying that she heard I'd been speaking unfavorably about her and she wanted to clear the air between us.

My friend had the most guilty look on her face. She tried to quickly deliver a persuasive essay as to why she said what she said, assuring me that she was not being phony.

Oh, the shadiness gets better.

I started seeing a guy she'd known before I did. So like any girl, I wanted the lowdown on him.

"I know he used to be a dog, but I think he's changed. Don't get too attached, though. Just have fun," she told me. I respected her candid advice and proceeded to get to know him.

She had just left out the part where she had been sexually involved with him. I found out only because he told me all about it. Actually, she said that she "forgot" about anything ever happening between them.

Years of double-crossing and deviousness let me see that I felt uncomfortable calling her my friend. I don't claim to be nor portray myself as mistake-free. But enough was enough.

When you're an ethical and authentic friend to someone, you expect reciprocity.

For years, people voiced opinions about our friendship. I always rebutted them. Some people are lost and lured by temporary pleasure in place of withstanding relationships.

At night, I always sleep well knowing that I stuck that friendship out for as long as I could. I hope that she has a successful career, relationship and life.

I also hope that she never gets her own messy friend, like the one she was to me.

Zahara Johnson's column appears regularly in b.