The first thing everyone should remember is that a habit takes time to get rid of. This means that you would need to be patient and consistent with the techniques that are designated to support positive behaviours. In time, you and your dog will feel more content and the habit will start shaping itself.
It might be that your dog is showing signs of aggressive behaviours towards both people and dogs without clear reasons. There are various training techniques for dealing with such behaviours.
Exercise is important to keep your dog happy as well as physically and mentally balanced, so one of the first thing would be to ensure he/she is getting enough time outdoors in a controlled enough environment such as a quiet park and on the lead.
The second thing you must do is research on your dog’s breed. Dog’s needs vary drastically and it is your responsibility as a good owner to make sure you are willing to understand your dog’s needs and typical behaviours. It will make your relationship with your dog stronger which is very positive.
Then it is easier to work with your dog using specific training techniques and leadership tips which will focus on overcoming fears and aggressive behaviours.