Make chapter priority list to study. Chose the important chapters first.
Don't spend too much time on a chapter. If you’re not comfortable then take help from your parents or teacher.
Breakdown the entire subject into small sections. Study each section at a time. Make sure you study lengthy and tough sections when you’re in a fresh mood. Preferably early in the mornings.
Take regular breaks. Preferably everyone and half-hour for 10-15 mins. During the break try to lie down on the bed listening to some good music. Strictly do not watch television, web series on the internet, no browsing of social pages or games.
Fill 4 bottles of water and put them on or nearby to the study table. Drink sip by sip continuously, this will give oxygen to your brain and all vital body parts.
Eat regular homemade food with no or little spicy. Avoid junk food. Take more energy food as snacks.
Expose to sunlight
This is a must to do an activity, every day before 10.30 AM. Take a walk out of your home to expose yourself with sunlight, and watch people keenly.
Sleep at least for 6 -7 hours without any disturbance. Don't watch a mobile device before you go to bed.
Keep talking to your parents, friends at least a couple of times in a day for about 10-15 mins. Talk to something interesting. Don't argue or debate topics that are not related to you. Keep away from them to save a lot of time.
Stretch your arms, legs, spine. This has a lot of benefits like improves to focus on studies. Walk and do warmup exercises at least for 7 mins a day.
Study to learn
Study to learn, when you do so marks will follow.