Projection bias is the tendency to over predict the degree to which our future taste is influenced by our current taste or liking.
An example will be buying a house in the summer that includes a pool will justify spending that extra cash. Since it is the summer, a pool will be great. However, they over predict the value of the pool. In reality the pool will be less used in the future because of season changes, maintenance and etc.
So by limiting projection bias, we can spend smarter.