Depends. If you take too much, you can od, and this is more common in people who have never used it before. If you inject it, you can get severe infections, including brain abscess, bone infections, heart valve infections, the aids and hepatitis viruses. If you use if more than 2 or 3 times in a row, you are at risk of becoming addicted to it. It is a crime, you can get arrested.
All Bad... There are no upsides to heroin use/abuse! whatever effects you are experiencing(and they are varied depending upon the individual and include euphoria, change in mental status, cardiometabolic changes up to and including death!) i would advise you to stop using! no good can come of it!