I have shared a flat with a few different people over the past few years and it always amazes how ridiculously hard people brush- I see them doing it and I cringe.
Hard is not good. Right is good.
If your toothbrush looks like you have used it to clean in-between the tiles of your shower after a few weeks or couple of months; you are brushing too hard. If you can see any areas of your roots that are exposed with no history of gum disease- particulary on your premolars, 1st molars and canines in that order; you may be brushing too hard, (or may have been at some point in the past). Your dentist will be able to advise you if you have any signs of wear and give you a gentle tap on the wrist, then point you in the right direction. Our toothbrush abrasion
section discusses this in considerably more detail.
If you brush too hard- try holding the brush as you would hold a pen- this makes it more difficult to apply excessive pressure. Remember plaque is a very soft substance and doesn’t need much effort to remove it- just a little pressure in the right place. If it's left long enough to turn into the hard tartar or calculus (most commonly found on the backs of your lower anterior [front] teeth), no amount of tooth-brushing will remove it; this is a job for your dentist or hygieneist and their specialized tools.