"Meditation is the soul's retiring of itself. A Christian, when he goes to meditate, must lock up himself from the world. The world spoils meditation; Christ went by himself into the mountainside to pray, Matt. 14:23, so, go into a solitary place when you are to meditate. "Isaac went out to meditate in the field," Gen. 24:63; he sequestered and retired himself that he might take a walk with God by meditation. Zaccheus had a mind to see Christ, and he got out of the crowd, "He ran before, and climbed up into a sycamore tree to see him," Luke 19:3, 4. So, when we would see God, we must get out of the crowd of worldly business; we must climb up into the tree by retiredness of meditation, and there we shall have the best prospect of heaven.
The world's music will either play us asleep, or distract us in our meditations. When a mote has gotten into the eye—it hinders the sight. Just so, when worldly thoughts, as motes, are gotten into the mind, which is the eye of the soul—it cannot look up so steadfastly to heaven by contemplation. Therefore, as when Abraham went to sacrifice, "he left his servant and the donkey at the bottom of the hill," Gen. 22:5, so, when a Christian is going up the hill of meditation, he should leave all secular cares at the bottom of the hill, that he may be alone, and take a turn in heaven. If the wings of the bird are full of slime, she cannot fly. Meditation is the wing of the soul; when a Christian is beslimed with earth, he cannot fly to God upon this wing. Bernard when he came to the church-door, used to say, "Stay here all my worldly thoughts, that I may converse with God in the temple." So say to yourself, "I am going now to meditate, O all you vain thoughts stay behind, come not near!" When you are going up the mount of meditation, take heed that the world does not follow you, and throw you down from the top of this pinnacle. This is the first thing, the soul's retiring of itself—lock and bolt the door against the world." (Thomas Watson)(From: Thomas Watson's A Christian on the Mount, link)