Unless I had believed to see,
The goodness of YHWH in the land of the living.
And finally he brings out the fact that he had almost been in despair. Had it not been that he had believed to see the goodness of YHWH in the land of the living, he could not have endured, such was the anguish resulting from his rejection. When our spiritual legs fail us it is good that we can look to the certainty that ‘the Eternal God is our refuge, and underneath are the everlasting arms' (Deuteronomy 33:27).
‘Unless I had believed.' We would expect something to come before this. Some add words in translation like ‘I had fainted unless --'. That is clearly the idea. LXX has simply, ‘I believe that I will see the goodness of the Lord in the land of the living.' Alternately he may be saying, ‘such as breathe out cruelty were it not that I believed to see the goodness of the Lord in the land of the living' with the idea that his faith in YHWH in some way prevents them from behaving in that way towards him. But it is undoubtedly very awkward.