The major point of that book is that people are driven more by a need for stability and predictability than they are by a need for happiness.
Freud noted that people who had been subjected to traumas spent their time and energy trying to regain the emotional equilibrium lost to that trauma, with the result that they remained emotionally frozen in time and unable to take advantage of opportunities to grow.
Freud generalized this point by saying that, although some people are trying to improve and change themselves, most are simply trying to find a way to avoid further disruptions to their emotional lives.
Freud conjectured that organisms have a desire to ‘die in their own way’, meaning that they wish to put their emotional affairs in order and then punch out. He even went so far as to posit the existence of a ‘death instinct’ responsible for this supposed death wish.
The first point—that most people, and probably most animals, are more interesting in achieving emotional stability than in achieving happiness and self-actualization—is good and accurate.
The second point—that organisms wish to ‘die in their own way’—is less good.
The third point—that there is a ‘death instinct’—is not one of Freud’s better ones and does not, in my experience, have much clinical or theoretical utility.
But it’s really about the first point, which is accurate.