Not letting go is a primary cause of all the inaction and denial we see in government and large corporations. Consumption of resources has the biggest impact on our ability to live sustainably. Consumption has been a necessary part of our form of economy. At the level of the individual, getting people to shift away from consumption and many other societal norms will require shifts in each person's consciousness. This is not a technical challenge. It is a spiritual challenge and will require an inner and personal transition. These are not matters that better technology will solve. These are matters of the human heart and spirit.
We are really good at solving technical problems but the problems we face are of a different nature. As Einstein said, "Our age is characterized by a perfection of means and a confusion of goals." Technology has been and continues to proceed unabated. There is no design or plan for our evolution into our technology. We don't know where we are going but we're good at getting faster.
We have lost our connection to the natural world. A rediscovery is in order and might lead us to being more able to address the spiritual challenge. Before the rise of science and technology when religions presided over a much slower moving and easily managed world, great thinkers of all persuasions saw that man's journey was a journey from the demonic to the divine and that history was somehow the stage of human redemption. That view died with the rise of secular capitalism and industrial democracy. Part of the answer is a rediscovery of our place in the natural world.
Hope is possible but I think hope is worse than useless if someone hasn't uncovered their sadness over the losses we are suffering. Many people will use hope to deny the reality of our predicament. Hope and hopelessness are two sides of the same coin. Both prevent you from dealing with your grief over the loss of 200 species a day becoming extinct, the loss of a clean and unpolluted environment. The loss of our bliss in thinking we had an infinite supply of energy to power the developed world. If you are not yet in grief over these losses, then you shouldn't be looking for hope. Start by examining something you have sadness over.
For those who have dealt with some grief over what I've described above then I think it is a good thing to talk about hope. I choose hope over hopelessness because it feels better and I think there are reasons for hope.