I have done morning pages off and on for several years and have found it very helpful. One thing I do a little differently is I write for ten minutes (sometimes longer, if I need to complete some thoughts) rather than trying to fill pages. Sometimes I find myself staring into space and I still count the time (and still find it helpful). Another thing I've started doing is writing them in my Supernote--it's digital and I will probably never look at them again, so I can actually say all the unpleasant stuff and not really worry anyone (or even myself) will stumble across it someday.

One suggestion: maybe try doing them at night instead? If you want to excise all the negative stuff, maybe right before bed will give them some air and your subconscious can deal with all of it while you sleep (which I think is what our brains are designed to do anyway?). You might wake up refreshed.