It is so good I’m copying the whole thing here (but don’t forget to check out his blog):
In a recent post I wrote: There are definitely upsides to [being a planner by nature] but the temptation to think of myself as captain of my own destiny, my protector, and my safe-keeper is not one of them.”
On rereading it today, I thought of Psalm 121 and Derek Kidner’s comments on it. Clearly the emphasis of this Psalm is on God’s keeping of his people. So of course, it would be idolatras for me to think of myself as my own safe-keeper.
He will not let your foot be moved;
he who keeps you will not slumber.
Behold, he who keeps Israel
will neither slumber nor sleep.
The LORD is your keeper;
the LORD is your shade on your right hand.
The sun shall not strike you by day,
nor the moon by night.
The LORD will keep you from all evil;
he will keep your life.
The LORD will keep
your going out and your coming in
from this time forth and forevermore.
(Psalm 121:3-8 ESV)
On verses 7 & 8 Kidner says:
The promise moves on from the pilgrim’s immediate preoccupations to cover the whole of existence. In the light of other scriptures, to be kept from all evil does not imply a cushioned life, but a well-armed one. Cf. Psalm 23:4, which expects the dark valley but can face it. The two halves of verse 7 can be compared with Luke 21:18f., where God’s minutest care (‘not a hair of your head will perish’) and His servants’ deepest fulfillment (‘you will win true life’) are promised in the same breath as the prospect of hounding and martyrdom (Lk. 21:16f.). Your life, in the present passage (7), is as many-sided a word as in Luke; it means the whole living person. Our Lord enriched the concept of keeping or losing this by His teaching on self-giving and self-love (e.g. Jn. 12:24f).
The Psalm ends with a pledge which could hardly be stronger or more sweeping. Your going out and your coming in is not only a way of saying ‘everything': in closer detail it draws attention to one’s ventures and enterprises (cf. Ps 126:6), and to the home which remains one’s base; again, to pilgrimage and return; perhaps even (by another association of this pair of verbs) to the dawn and sunset of one’s days. But the last line takes good care of this journey; and it would be hard to decide which half of it is the more encouraging: the fact that it starts ‘from now‘, or that it runs on, not to the end of time but without end; like God Himself who is (cf. Ps 73:26) ‘my portion for ever’.