It is very easy to feel unmotivate, because here in br research money is not always there, the scolarships are low ( as in anywher in the world), and you know that you not gonna make huge money for the rest of your life.
But as I said, it is a challange and a comitment, so you have to push through this difficulties and keep going.
By the end, to see your work published and your name there is what pays off. So when i am unmotivate i think about how cool would be to have my work published in a great journal by the end, to see my results in a great thesis.
This goals keeps me moving i think.