The reason men want to believe they have complete freewill is because of sinful pride.
We mortals need to feel that we have the final control over our lives. Although we talk as though we defer to God, we actually want to retain the final determination, saying that God has delegated his judgment to us, allowing us to save or damn ourselves. We won't accept that there is anything we can't understand, and we can't accept that we don't control everything--given enough time and effort to work on it. This was Adam's sin, if you remember.
But when we finally accept God as the supreme being and not as some celestial scorekeeper or "facilitator," when we stop trying to make him into our own idea of how a divine being ought to operate, we come to the ultimate understanding that He is in charge of all things, our eternal destinies included.
Then we know peace and joy in him, relieved from forever worrying if we've done enough to save ourselves or even if we know how much is needed.
Freewill is a theory not unlike the Ptolemaic view of the Universe, full of unexplainable processes and numerous contradictions that have to be fixed with patches that are exceptions to the theory's own rule. Otherwise it doesn't work. And it provides no idea at all about how to use that supposed freewill in order to earn salvation. It's a general statement with no coherent parts.
Believing the Bible's teachings on Election, however, does away with that view of life in which we stumble around in the dark for a lifetime, trying to do good, hoping that the bad doesn't outweigh it, hoping that what is done is acceptable to God as being good enough,and never knowing what actually counts. God's eternal plan of Predestining men to salvation despite their inherent unworthiness is mercy indeed! What's more, this eternal design not only liberates us from this confused freewill treadmill that doesn't go anywhere that we can depend upon, but it's also consistent with everything we know of God--his mercy, his justice AND his sovereignty. For what kind of sovereignty is there if everything is undecided and uncertain in his universe as it relates to the work of his divine Son?
Then it is that we live for God instead of for ourselves, no longer trying to scratch out salvation but not knowing how to accomplish it.
We no longer think we might be able to curry God's eternal favor by way of doing little deeds we hope he likes enough to admit us to heaven. We have learned to "let God be God."