For thus said the Lord God, the Holy One of Israel,“In returning [repentance] and rest you shall be saved; in quietness and in trust shall be your strength.”But you were unwilling, 16 and you said,“No! We will flee upon horses”;therefore you shall flee away;and, “We will ride upon swift steeds”; therefore your pursuers shall be swift." Isaiah 30:15-16 (ESV)
These two verses wonderfully and succinctly sum up God's relationship with Israel (in this instance, Judah specifically) in the OT. He continually offered his provision and salvation, and they continually attempted to save themselves.
Unfortunately, this is how we today often attempt to live our lives. We really aren't much different than the Israelites. Our salvation (whether eternally or in a specific situation) cannot be gained of our own accord. Rather, salvation is only to be had through repenting and trusting in the Lord.
Our amazing and wonderful God continually offers salvation, but in many instances we simply aren't willing to trust in Him. The result, of course, is failure, and often with it a great deal of pain, hurt, and distress.
As believers we must come to grips with the reality that the key to victory in life is not found in ourselves, but rather in resting and trusting in the grace of God. When we do this, He delights to show mercy and rescue us, every time!