I tried mindfulness briefly - or at least the sitting-thinking-about-nothing exercises that are supposed to be a Vital First Step. I found it a) dull and b) realised I'm very bad at thinking about nothing. Since the point seems to be to help you concentrate and I really don't have any problem concentrating (possibly the opposite, at the same time I was trying to use pomodoro to stop myself getting too Engrossed in One Thing when I had lots of other things to do as well), I decided it probably wasn't worth worrying about.

I'm kind of dubious about the benefits on being of being able to think about nothing for extended periods - even it means you should get better at thinking about something for an extended period.

NB. You're not actually supposed to think about nothing, you're just supposed only to think about your own breathing. My own breathing is almost as dull as nothing, in my opinion.