Google offers this definition, which I particularly like: not prevent or forbid; allow. I see how my flesh does the prevention part of trying to get in the way of the Spirit flowing through me and directing me. For allow, I imagine a car driving down the road and me holding my arms out to keep my kids back -- allowing the car to pass. I have to (need to) hold my flesh back so the Spirit can keep going without hindrance.
While I was going through hundreds of verses with the word let in them, I noticed something. God is the person doing the letting action only once in all the New Testament (that I came across)! [Actually, it is Him not letting or allowing something.]
Man (me, you...) is to do the rest of the letting. Here is a very small sampling:No temptation has overtaken you except what is common to mankind. And God is faithful; He will not let you be tempted beyond what you can bear. But when you are tempted, He will also provide a way out so that you can endure it. 1 Corinthians 10:13
Therefore do not let sin reign in your mortal body so that you obey its evil desires. Romans 6:12
Since we live by the Spirit, let us keep in step with the Spirit. Galatians 5:25
Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen. Ephesians 4:29
Only let us live up to what we have already attained. Philippians 3:16
Let the peace of Christ rule in your hearts, since as members of one body you were called to peace. And be thankful. Let the message of Christ dwell among you richly as you teach and admonish one another with all wisdom through psalms, hymns, and songs from the Spirit, singing to God with gratitude in your hearts. Colossians 3:15-6
So then, let us not be like others, who are asleep, but let us be awake and sober. 1 Thessalonians 5:6
let us draw near to God with a sincere heart and with the full assurance that faith brings, having our hearts sprinkled to cleanse us from a guilty conscience and having our bodies washed with pure water. Let us hold unswervingly to the hope we profess, for he who promised is faithful. And let us consider how we may spur one another on toward love and good deeds, Hebrews 10:22-4
Who is wise and understanding among you? Let them show it by their good life, by deeds done in the humility that comes from wisdom. James 3:13
Dear children, let us not love with words or speech but with actions and in truth. 1 John 3:18Let is so interesting! It is more than just a passive action in these passages -- I'll sit by and "let" this happen. But it's not really a word associated with power or command, per se -- man up and do it! (which is likely why let and God aren't really associated, because He does have all power and command!) It's more of a gentle plea or urge with a strong, encouraging undercurrent -- please, for your sake! It's a man appealing to man.