v1-3: Man is hopeless is the face of oppression, compare Job 3. His conclusion is that he thinks it better never to have been born.
The reality of injustice, that power is in the hands of the oppressor. This has always been the case and will continue to be so, until Christ returns.
v4-8: The vanity of labour and achievement, since they often spring from an attitude of envy and greed and pride; at the same time there is complacency and loneliness. Again, we see that work without faith in God is vanity.
The powerful image in v6 is enhanced by the different Hebrew words. One handful with quietness is one open hand. In contrast two handfuls with toil is two grasping fists.
v9-12: The value of friendship and companionship; this is especially true in Christian service. Their companionship is "a good return." One can encourage the other; at night, two men can lie close to keep warm; in conflict one can defend the other.
Friendship gives us productivity, stability, intimacy and security. No wonder God told Adam it was not good that he should be alone.
v13-14: How sad that a man will be admonished no more, for he has ceased to learn.
v15-16: Although the second youth had become popular, the later generation forgot him, see Ex 1.8; Judg 2.7-10. Human memory is frequently selective memory; like the children of Israel who had testified to preferring life in Egypt! It is ironic that, when Rehoboam, Solomon's son, becamse king, that the people forgot the benefits that Solomn had brought them (1 KIngs 12.4).