alert! p/s: my english is so good *sarcasm*, but whatever i will tried to write in english either, theres a "proverb" said "you learn more by practicing" so yeah  

no story but heres my advices.

here my advices.

1) i suggest you to not to take modafinil (thinking you could focused more by taking modafinil? nah *being prejudice over here* , it might be placebo effect) take 1 cup of coffee is enough, sleepy? take cold shower or take a nap for 15mins)

2) you might want to try practice meditate. well at least, 5 mins a day is enough i think. (default mode for your brain!)

3)consume less sugar or non at all, yes avoid candy while you read or tried to learn something new aka reading HOW-TO books  . (chemical reaction in your brain, dopamine triggered by the taste of SUGAR, taste delicious, yummy! yummy means more brain activies in your brain)

4)avoid looking up for smartphone when you wake up (first things you do when you wake up is checking notifications, could trigger anxiety because you was waiting for notifications since the night you sleep, if you said you not checking for notifications youre a liar! then why the heck you checking your phone? wanted to check time on your phone? buy wall clock instead, its like a "morning GIFT" and the next day you wake up you get none, ANXIETY TRIGGERED!)

5) avoid shaking your legs when you studying, reading, or writing. (self explanation, SWEATING!)

6) plan activity for the next day you wake up. (decision fatigue *ehem* pls google) avoid unconscious time wasting activities, without you realized you just spend 10mins of instagram scrolling.

7) avoid consume too much information (see below)
Digital Dementia[B]

less information means more focus on important topic.

there you go 

btw, whats your passion?

hit me up! if you found out my english writing skills is amazing! goodluck