according to Cambridge Dictionary: constrain /kənstreɪn/ verb [ T often passive ] = to control and limit something . ex: The country's progress was constrained by a leader who refused to look forward.
restrain /rɪstreɪn/ verb [ T ] = to control the actions or behaviour of someone by force, especially in order to stop them from doing something, or to limit the growth or force of something
ex: When he started fighting, it took four police officers to restrain him.
[ R ] She was so angry that she could hardly restrain her self .
You should try to restrain your ambitions and be more realistic.
Growth in car ownership could be restrained by increasing taxes.