It seems it's about pride:
Psalms 131:1 HCSB
Lord, my heart is not proud;
my eyes are not haughty.
I do not get involved with things
too great or too difficult for me.
Psalms 131:1 NASB
O LORD, my heart is not proud,
nor my eyes haughty;
Nor do I involve myself in great matters,
Or in things too difficult for me.
Psalms 131:1 MSG
GOD, I'm not trying to rule the roost,
I don't want to be king of the mountain.
I haven't meddled where I have no business
or fantasized grandiose plans.
neither do I exercise myself in great matters; or, "walk" (m) in them; these were not the subject of his employment and conversation; he did many great things, in killing the lion and the bear that came into his father's flock; in slaying Goliath with a sling and stone only; in leading out the armies of Israel, and slaying his ten thousands; and he exercised himself in the great things of the law, which he was careful to observe, and studied the great things of the Gospel, which he had the highest esteem of, and desired to understand; but he did not seek human greatness, or the great things of this world, for himself; he had no ambitious views, or was desirous of the kingdom he was anointed to, before the proper time; see 1Sa_18:18;
or in things too high for me: or "too wonderful" (n); see Job_42:3. He contemplated the wonderful make and frame of his body, the texture, symmetry, and use of each of its parts; he observed the wonderful providences of God towards him ever since he had a being; and particularly he took notice of the wonderful love of God to him, and remembered and talked of, and declared, the wonderful works of grace and redemption; but not things above his capacity, out of his reach, and which are secret, or not clearly revealed: and such things we should be content to be ignorant of, or not to have adequate ideas of, or be capable of accounting for;