A response to the "small group questions" for the 10 February 2019 message at First Pres, Boulder. 
Now that their father was dead, Joseph’s brothers became fearful. “Now Joseph will show his anger and pay us back for all the wrong we did to him,” they said.
So they sent this message to Joseph: “Before your father died, he instructed us to say to you: ‘Please forgive your brothers for the great wrong they did to you—for their sin in treating you so cruelly.’ So we, the servants of the God of your father, beg you to forgive our sin.” When Joseph received the message, he broke down and wept.Then his brothers came and threw themselves down before Joseph. “Look, we are your slaves!” they said.
But Joseph replied, “Don’t be afraid of me. Am I God, that I can punish you? You intended to harm me, but God intended it all for good. He brought me to this position so I could save the lives of many people. No, don’t be afraid. I will continue to take care of you and your children.” So he reassured them by speaking kindly to them.
excerpt from the New Living Translation of the book of Genesis 
What can you recall about the life of Joseph that may have led to a life of more generosity? Or perhaps less generosity?
I don't really accept the premise of the question. Joseph's generous spirit wasn't the result of life circumstance outside of his control; but his response was an act of faith irrespective of his life or circumstance.
When Joseph says "You intended to harm me, but God intended it all for good." he is declaring his faith in God's plan for his life. It is faith in God's character as shared by Jeremiah:
"I know the plans I have for you,” says the LORD. “They are plans for good and not for disaster, to give you a future and a hope." 
Faith in God is not a response to blessings in our life, nor is it in spite of trouble. As it was for Joseph, faith is the source of perspective. It is faith that led Joseph to see his circumstance as the work of God, and for good; not the serendipity of the end result.
What are the circumstances in your past that may be negatively effecting a life of generosity in the present?
From the literal intent of the question, there are none. I am blessed beyond reason, and have tried to live generously.
If there is a tangential critique for me here, however, it may be that I have become more hardened, less charitable, and (from a certain perspective) less generous with those who, thought I once saw them as mentors in the faith, have fallen short of our outright rejected the teaching that I received from them.
How does Joseph overcome his own circumstances, and what are the lessons he has learned the we meet be able to apply to our own situation?
Joseph did not so much overcome his own circumstances as he remained faithful to God, and God used Joseph for his own purposes. By God's grace Joseph was saved through faith, and so are we. 
If we did apply those lessons to your own situation, how would it alter your generosity and sense of abundant living?
We suggested three things from Joseph's life that may help our own generosity regardless of circumstance (careful stewardship, extra-ordinary service, and bountiful grace). Where do you already exhibit these things, and where do you need to take a deepening step?
I will abstain from puffing myself up by congratulating myself for success; but I will simply say that my stewardship is pretentious to care but often ultimately lazy; my service is ordinary, but I generally accept that as my calling, at least for right now; and I will, as I said before, be trying to be more gracious than I sometimes become.