Any rational and scientific view of the assembled facts, including the sixty plus tipping points that have been tipped, the increasing release of methane, and the potential loss of our ability to grow food as temps rise and growing conditions change would suggest that human extinction is a real possibility.
I think that facing the feelings about such a possibility is important and healthy. Shoving the feelings away, ie denial, is unhealthy and leads to a false view of the situation. One example, that of having hope that renewable energy will replace the energy found in fossil fuels is unfounded. I think renewable energy is part of the future but it won't supply the same quality and quantity of Joules (units of energy) that oil does.
Having non-rational hope prevents you from experiencing your grief over a situation. That can lead to ineffective action. If you feel the pain then you can see past it and take actions that actually make a difference.
Once you have experienced your grief over our predicament, there's more on the other side of grief. I think it's possible to find some real hope. I feel hopeful now because I have and still do take action with others. I have helped to build a community of people who are taking action. I remain unattached about the results but it feels good nonetheless.
Some additional reasons why there's more beyond the conclusion of extinction. First, humans are really bad at predicting the future. No expert really knows how this will all turn out. Second, the idea that facts are slippery creatures. Any scientist will tell you that they modify their positions based on new experimental evidence and so with time what was "true" can change. There was a time when most people considered it a fact that the Earth was flat. With enough time facts can change.
Third, our culture is steeped in rationality. So much so that it might be impossible to take in this next idea. There are other ways of being that don't involve rationality and they are just as valid as rationality. For example, intuition, beauty, nature, currently unexplainable phenomena and miracles. Miracles to me are things we can't explain from our current perspective. These things and more make up our non-rational world.
Finally, consider that anger and other negative emotions have long term health consequences. Dealing with negative feelings is a step toward a healthy life. There don't seem to be any long term health consequences caused by carrying too much happiness.