Mental dependency in other words could be called as mental salavery. When someone is mental slave he or she will not be able to get through the ups and downs in the life. As there is famous quote
Death is better than slavery.
Slavery does not mean that we are in control of other only physically but some time we are mental slave.
Mental slavery is more worst than physical slavery.
Being a mental slave, we have not our own ideas and are not able to think about the problem with our mind and we are reduced in certain limit and not allowed to cross that limit.
Mental slavery also leads to aimless life because we don't have our own aim instead we are like robot that just have to follow the orders of controller.
So we shouldn't be a mental slave and lead a life full of freedom. Such life provides us the path and determination to fulfill our dreams in better way and there will be nothing in this world which we couldn't achieve.