There are a number of reasons why a juice can be too harsh. One is the type of atty, resistance you are using. A sub-ohm coil will make your juice way too harsh. It could also be from the amount of nicotine you use. It might just be too high for your tastes. It could also be the quality of the nicotine. Some vendors use a lower grade of nic, to cut costs, and it can be harsh or peppery to some. The best way to dilute it is to get the same juice in 0mg, and dilute it that way. You could also use USP VG, but that will cut into the flavor, as well as the nicotine.