Let us take up a child. We find that without any instigation the child is interested in worldly matters. It learns movie songs quickly, it enjoys games, it watches cricket match and such other worldly matters. Who forces the child to do all these? If a small child gets interested in such matters without being compulsorily taught by others, it only goes to show the nature of the manas.
The nature of the manas is only to move towards worldly matters. Since the child has vasanas of innumerable births, the manas moves towards the world. Our manas will not come under control within a ten days or a month's dhyana/japa or any amount of other spiritual practices.
However, we cannot give up our attempts for this reason. What is the reason for the inability to bring the manas under control so easily? We have taken innumerable births in which the manas has always moved towards the world. This manas will thus not come under control in an hour or within few days or months? It will keep running towards new vasanas. That is its nature. But, we have said that while even worldly 'vidhya' (education) needs a Guru (spiritual Master), 'adhyãtmika vishayas' (spiritual matter) certainly needs a Guru. We have said that one who has no Guru is an orphan.
The main purpose ('parama prayojana') and use of embracing a Guru is to turn our manas inwards. The reason for this is that only when our manas moves inwards will there be spiritual progress. Otherwise, there will not be any progress.
Please check these: Excerpts from a discourse by our Sri Sri Muralidhara Swamiji