There are Four Known Ways:

Meditation is bane for all stress. Through meditaion one discovers his true identity. Many think meditation is a way to control thoughts. Meditation had been practised by our ancestors, thousands of years back so they could raise the consciousness and lead a...

YOU have to change your non - assertive behaviour to stop others from manipulating you by learning and practising

The difference is an assertive person may not be self-confident but a self-confident person is always assertive