Motivation to do a ton of homework?

[math]

Motivation comes from the fact that someday when you get a degree, you will get a good paying job.
So the prospect of your education helping you make money is perhaps the biggest motivating factor.

I was deceived and cheated by keeping such motivation, because I turned out jobless despite being a post graduate in my field. The feelings of betrayal still exist deep inside of me.

But you are 15 only, you have lots of time at such age (you don't need to work at all) and a lot of resources too (your parents and friends). They should motivate you