I recalled a dharma talk by Ajahn Thanissaro Bhikku on Youtube. In it he compared mindfulness and meditation to a skill. And like anything else in life you need to practice to become good at that skill.
At the beginning your mind is full of its habitual mess of cravings, frustrations, anger, hate, distractions, torpor, conceit, because you never experience anything else you don't even realize its a problem. Maybe you dull your constant mental irritation with alcohol, media or computer games.
As you started to meditate you experience immediate withdrawal from the senses, you want to check your phone, play with computer, go watch tv. It's agonizing.
However as you push through the practice, and the mind begin to settle, things become clearer, your mind feels lighter, there are moments where you feel like your heart has opened up and great peace and joy occur and its wonderful. You even made some realizations about your life and habits. It's like a fog has lifted. And you become horribly aware of the bad things you do that keep you in a state of constant confusion, craving and anger. This is mindful concentration.
Unfortunately this happy state won't last, back into the world and you realize your personal annoyances and irritation is still with you, but meditation becomes your safe space to let go of the annoyances.
So you work hard to get better at this process. If your mind was a glass of cloudy muddy water before, meditation was letting it becomes settled and clear. What you need to do next is fish out the sediments, and you do this through the application of wisdom, for example using compassion to let go of hate, using generosity (Dana) to let go of greed. Awareness of impermanence and selflessness become your arsenal.
Of course meditation is only one branch of the Noble Eightfold Path - concentration. You need to follow up with the rest, with better wisdom and ethics which will allow you to have better concentration.