When it comes down to your product, you just want it to work - not just in the sense of all of its features operating properly, but you also want it to resonate well with your intended audience. You want them to love what you've created. They should feel like it has enhanced their lives. Whatever it is you've made, make sure that your creation avoids a few mistakes product designers inadvertently make during the process, so everything works as well as it possibly can.