Complicated...

My best friend is constantly ranting to me about her troubles with this boy that she has been seeing (on/off) for almost a year now and it's getting a little repetitive. It always begins with her crying to me about how he's such a jerk because he didn't do something she wanted him to do or he didn't respond the way she expected him to.
I then comfort her and spit out the honest truth about how he is a total jerk and that she needs to swallow her feelings and think with her head.

Then, for a slight moment, she nods in agreement and promises to cut relations and contacts with him.
My best friend then cuts any form of communication with him but then reconnects with him in about a week and the cycle starts all over again. I'm sure you get the picture and know exactly what's happening.

So then she's caught in this never ending cycle of happiness/unhappiness. My comments to her get more and more bitter but the same thing happens again. I know that she is totally in love with this guy, and yeah sure, all the bollywood songs claim that you need to follow your heart, but in all honesty, what does your heart know? There are times in your life where you need to make decisions with your brain and figure out what is right and what is wrong despite what your heart is telling you. You may agree or disagree with this observation, and that's fine because ultimately, I'm in slight disagreement with this observation, too.

I realized that despite what I'm saying to my friend, her decision to go back is not exactly dumb, because we all do it. Even I am a hypocrite and go against my own will and fall into the cycle, too.

Have you ever been caught in the cycle of happiness/unhappiness? If you were, how did you get out? Also, how do you deal with a friend who asks you for advice and ignores it?