How do you stay motivated to practice?

Hello! Im 17, im from Argentina. I play bass. Lately Ive been having a hard time on practicing, i get bored quite quick and im not finding the point of it anymore. Playing bass and specially jazz is what i want to do of my life. Any advice to get over this? I had times like this on the past but in a couple months i have a big exam to try to get in a really good music school, and should be practicing way more. Thanks!