Good concentration is a must if you want to maintain solid study habits. Internal factors(worry, stress, lack of confidence, even hunger and fatigue) and external factors (noise, lighting, and physical setting) greatly affect your concentration. Like other skills, concentration can be learned with practice.
10 Online Tools for Better Attention & Focus provides "distraction management" apps.
How to Improve Your Concentration explores how everyone's brain is a "solution finder," and we all have to work on focusing our concentration.
How to Improve your Concentration when doing Homework or Studying offers five tips for improvement.