Humanity tends to project its own faulty habits onto God. This is especially true regarding the nature of His love. We think we must barter, plead, or try hard to earn the Lord's favor. But as the prodigal son learned, the Father's love is unconditional.
The wayward son expected his father's love to be diminished. Therefore, he went home hoping for a place among the family servants. Imagine the boy's delight when Dad greeted him with a hug and a celebration. His actions certainly didn't merit an outpouring of affection, but Jesus' parable is all about a Father who doesn't give people what they deserve.
A love based on conduct would keep people guessing, Have I done enough? Instead, God cares for you simply because you're you, and He expects nothing in return. Consider the prodigal's life after his homecoming party. He didn't move into the servants' quarters and get to work. He was reinstated to his place as the second son of a wealthy man, with all of the privilege that entails. In the same way, believers are the Lord's cherished children (2 Cor. 6:18). When God looks at His loved ones, He doesn't focus upon past failures, faults, or sin. He sees the heirs to His kingdom—men and women who love Him and desire to spend eternity in His presence.
No matter how far we may wander from the Lord's perfect will for our lives, we are always welcome back. The Bible teaches that God's love cannot be lost, regardless of sin or poor decisions (though we may have to live with the consequences). Our Father's arms are always open.