Another idea: The Serenity Prayer, slightly reworded to use optative / passive voice?
"May I have serenity to accept the things I cannot change..." and so on? Works as a request as well as a statement of intent.
That would work if you replace God for I'm thankful/grateful:
I am grateful I have the serenity to accept the things I can't change....
and I'm thankful that I will not give up on what I think is right even though I think it hopeless.
I like Saint Francis prayer:
I am an instrument of peace
Where there is hatred let me sow love.
Where there is injury, pardon.
Where there is doubt, faith.
Where there is despair, hope.
Where there is darkness, light.
Where there is sadness, joy.
May I not so much seek to be consoled as to console.
To be understood, as to understand.
To be loved, as to love.
For it's in giving that we receive.
And it's in pardoning that we are pardoned.
And it's in dying that we are born into a fulfilling life.