It is a pretty bold claim to say that knowing your measurements will change your life, but it will.
Knowing your basic measurements (bust, waist and hips) will up your DIY game and mean that you can online shop like a BOSS. Once you know those numbers you can look at a sewing pattern and see that yes it will fit with no alterations or no it will take some pattern re-jigging to make it work. On top of that retailers often put the dimensions of a garment in the descriptions or have a size chart you can refer to. So knowing your measurements can mean the difference between most things fitting and having to return your entire online haul.
It really helps to have a non-judgy friend or family member measure you up. You can see how easy the process is here: