Boredom can sometimes come down to

a) Strugging / lack of understanding of more difficult concepts in a subject

or

b) They're not engaging enough for you

The only thing I can think of to say is really push yourself, give yourself a challenge, see how far you can go in the subjects that are of interest to you.

Even if they're not particularly of interest to you, give it your best shot - don't wait for the motivation to arrive - because it might never .... but good athletes? They wake up every morning with their shoes and their running clothes out already from the night before - they put it on - and they get out there and they go. Their end goal - finish the race in the fastest time.

What is your goal?

To achieve well in certain areas?

Work on your long term goals and try to focus on these.