I was stuck on open chords for awhile just because they're so easy to reach for. One thing that really helped motivate me was to find a song that I loved that included barre chords that I really wanted to learn to play, and then playing along to a live track of it (for the energy). That did it in terms of breaking through the mental barrier.

I used Back Home Again (there's a great live version on the Live in London album), but any song you love that has a handful of barre chords sprinkled in will do. Key of E is good for this because of the F#m and B, which are more or less required learning if you want to be able to play beyond the basics.

Also find something with a bass note strum pattern (again, Back Home Again works great for this as does a lot of country stuff), because the bass note gives you one extra beat to grab the barre chord... ;-)

My other big tip that made barre chords click for me and seems to work for others is, put your chord fingers down on the fretboard first and put the barre finger last. I know that's not the technically preferred way, but try it and see if it doesn't make the whole situation much easier.