Do you recognize in your question the spirit of the questions Paul writes in Romans 9: “Why does he still find fault? For who can resist his will?"Is it God's fault if somebody doesn't come to Him?
You will say to me then, “Why does he still find fault? For who can resist his will?” But who are you, O man, to answer back to God? Will what is molded say to its molder, “Why have you made me like this?” Has the potter no right over the clay, to make out of the same lump one vessel for honorable use and another for dishonorable use? Romans 9:19–21 (ESV)
FWIW, I am confident that no one is sent to hell that has not chosen to go to hell. Left in our natural condition, we are all by nature children of wrath and willingly choose to reject God's salvation. Just like unrestrained water flows downhill, we, without God's intervention, will pursue sin and live in the passions of our flesh. But God chooses to be rich in mercy and makes some us alive together with Christ. Ephesians 2:3-10 (ESV)
What the Bible refers to as boasting is not the equivalent of pride. One type of boasting that is spoken against in the Bible (there is boasting that is allowed) is when a person is able to take credit for some aspect of their salvation, e.g. Ephesians 2:8-10 (ESV)The "prize" is available to all, so whatever you decided is boasting is merely the reception of God's gift.
I wasn't "proud" of anything when I unwrapped my Christmas present, so I don't see how pride figures into your thesis.
Regarding your Christmas gift, you rightfully can "boast" that the only reason you now have your Christmas present is that you accepted it. You could have not accepted it and tossed it in the trash. So your actions were absolutely necessary for you to now have your gift.
I do agree that acceptance is part of our salvation process. But I am also asserting that I think that it is a work on God's part to cause us to see, desire, accept, and obey the Gospel. From beginning to end, He is the cause of our salvation. We have no reason to boast.