“For in many things we offend all. If any man offend not in word, the same is a perfect man, and able also to bridle the whole body.”
James 3:2

In the main verse, he says you might make mistakes in a lot of things, so instead of focusing on trying not to make mistakes in so many things, focus on the one thing that is needful, exercise yourself to always be found in the word of God, and when you do, you would influence your whole life and those mistakes you might make in a lot of things would become non existent. Luke 10:38-42
So believe Jesus- paying attention to the word is the one thing needful, exercise yourself in the word:
“For bodily exercise profiteth little: but godliness is profitable unto all things, having promise of the life that now is, and of that which is to come.” 1 Timothy‬ ‭4‬:‭8‬ ‭KJV‬‬
How many times did God, before he sent the army of Israel out to war, insisted that they must train their muscles and be physically sound before they left for battle? To God, those things were not a factor in their success; his word was the only determinant for their success, so instead of trying to perfect a lot of aspects of your life at once; give yourself wholly to God’s word.