Concentration is the key to self-mastery and to your ability to access higher levels of knowledge/consciousness and deeper states of awareness. But before you can master concentration (Dharana), you must first start developing an understanding of yourself on subtler levels within the tangible/physical dimension. This understanding can best be obtained through mastery over your senses.
To gain mastery over your senses and to become a conscious participant in your life, someone who has the ability to control the different aspects of your being in deliberate ways, as opposed to becoming controlled by the people and influences outside of you, or the emotions and unaware thoughts that you generate due to mental distortion within you, you must first cultivate awareness of your actions (through Yamas and Niyamas), your body (through Asanas), your breath (though Pranayamas), and your senses (through Pratyaharas). This cultivation of awareness will empower you to avoid becoming trapped in patterns of unconscious behaviors based on ignorance.
To put it plainly, lack of self-control and possessing little self-awareness as you navigate through the world can easily lead to behaviors that create imbalances that lead to suffering in your body, mind, and spirit, and can lead to senseless Karma (actions that have a cause and effect in the world), that makes it virtually impossible for you to effectively create the inner peace and meditative state (Dhyana) required to reach your goal of Samadhi. So, to avoid becoming trapped in unconscious behaviors, you must first develop self-awareness and self-control.
Whether it is something outside of yourself like your phone, the internet, other people’s behaviors, or a distraction that you create within yourself like heavy emotions that come from negative thinking or belief patterns, and so forth, any neutral thing, without lack of awareness and self-control, has the potential to turn into a distraction in your life that takes you off of your path unless these things are engaged in with self-awareness and self-control that supports true long-term concentration on your goal.