Is it ok...?

Is it okay keep stuff from your boyfriend or girlfriend? Similar to the the common expression, "everyone has their little secrets?" I hear some of my friends tell me stuff that they've thought, said, or done that they haven't told their significant others. Yes it is stuff that their boyfriends or girlfriends wouldn't be happy to hear but shouldn't be upset about but probably would, especially since they have kept this stuff from them for so long. I feel it's stuff their other halves should know but as their friend it isn't my place to say anything, much less cause a rift in their relationships.
Just to ensure trust, I try to tell my boyfriend everything: the stuff I'm not proud of, the stuff in my control, the stuff that's not, and the embarrassing stuff. That's because I feel it is his right to know and I want him to do the same to me. If everything is out in the open, you have nothing to hide.

"So make me promises, girl, the kind I know you can't keep
And while I'm losing my mind, I hope you're home finding sleep.
But you and I both know that that's not the case
Because the look on your face gives all your secrets away."

-One Hundred Times by Hit The Lights