This is a repeat tip - but one that is a very common mistake I hear every day. As a blanket rule - DO NOT brush your teeth within 30min of eating. This is especially important if you have consumed something acidic. When you eat or drink something that is not water (this includes, lemon water, flavoured water, soda and sparking water)—it takes 30 minutes for the natural bicarbonates in your saliva to return the mouth to neutral. In that time your teeth become soft, and if you apply force, you will quite literally brush your enamel away which does not grow back. Try brushing before breakfast (perhaps in the shower) and follow your breakie with water or chewing gum (sugar free!).