It appears your are health consious . Good.
Schedule your activities
Plan your work (studies) so that it is feasible
Have time for physical exercise (Brisk walk 20 min in morning ) in your schedule
Do not hesitate to get help from seniors to plan your preparation
For improving concentation:
Go for regular Relaxation Techniques
: Breathing Exercise
JPMR (Jacobson Progressive musle relaxation technique ) is useful
All the Best!