for he has been good to me."
This is the end verse to Psalm 13 and it makes no sense if you actually read Psalm 13. The Psalmist begins in lines 1 and 2 "How long, O Lord? Will you forget me forever? How long will you hide your face from me? How long must I wrestle with my thoughts and every day have sorrow in my heart? How long will my enemy triumph over me?" This is a LORD that is good?
But this is what it means to trust in the LORD. David was clearly depressed and anxious, and yet through thick and thin he trusts in God. He never gives up hope because he knows who God is. He trusts in his salvation and his unfailing love, even though it seems his love is failing. And he nonetheless sings his praises as he reflects on every good thing God has given.
In your depression, remember your blessings. Jesus, while dying on the cross, also sang the opening lines of Psalm 22, praising God in his distress because of the salvation he trusts in even though he lay dying and knew he would not survive. And what did God do? He raised him to life and saved him even from death! Death is not the end for those who trust in the LORD's salvation and sing.