Lindley Saffeir for Maine Conservation Voters writes:

“Anxiety” by kevin dooley is licensed under CC BY 2.0
Saffeir provides ways t0 overcome the anxiety:
Many of us who are conscious of climate change are also aware of what we could be doing as the “ideal climate activist” – reducing our driving time, avoiding air travel, eating a vegan diet – the list goes on and can feel overwhelming and unachievable. Kastner suggests that, “just like all habit change, the best policy is to choose something small enough that you will succeed at but large enough to challenge you.” Set a limit on how many miles you are comfortable flying in a year. Limit your meat consumption to a number of meals per week. Make these actions quantifiable and clear. What takes the least amount of effort and will make the most impact? Is it spending hours biking to work or using that time to call your representatives to push for more progressive climate action? It is important to decide what feels meaningful to you, and to then commit to it.
She also provides suggestions to deal with white guilt, anger and hopelessness, including this from Kastner:
When you are helping others, or working in solidarity with others towards a common good, your body releases oxytocin, the ‘tend and befriend’ neurochemical.” The climate movement, and other deeply intertwined political movements that are ultimately rooted in justice and empathy, can carry a spiritual lift that compensates for the setbacks and struggles.