Think critically ruthlessly. Courageously. Embrace mindfulness (radically accept reality as it is). Voluntary discomfort, patience, and gratitude. Develop your perspective. Develop your strength of character.
Eliminate unnecessary suffering ruthlessly. Reject hedonism. Reject escapism. Reject distortion. Reject toxic striving, toxic ambition. Manage your psychology.
Find meaning where you can. Know your limits within the human condition. Have some humility.
This life is inherently meaningless and absurd, full of arbitrary, severe suffering/misery, severe pain, stress, and anxiety. The suffering is distributed arbitrarily (eg. an innocent woman born into a North Korean concentration camp). We live in a world that is blatantly blind, cruel, unjust, immoral, and unethical.
I used to value optimism more than intellectual honesty. This was in large part, a survival instinct that I've had to override gradually (as I strengthened my nervous system, subconscious, intuition, and such). Now, I value ruthless intellectual honesty far more than a bias for optimism.
Watch: Daron Larson's talk on mindfulness.