The key thing to keep in mind is that slaves and slave owners had entirely unique lives. We tend to generalize the experience of both parties based on what would be common, but that's not to say there wouldn't be outlying cases of slavery that did not fit the common narrative.
That being said, even in cases where an enslaved person would be treated in a humane manner there is that very harsh reality that American chattel slavery revolved around one simple fact: lack of free will. Even in New England, where you see the enslaved often doing skilled labor or even being educated, you still never had freedom to act as you willed if it did not benefit the person claiming ownership of you. On one end this could be as simple as not having a choice where you lived; in others such as a sale ad in Boston, it could be the sale of your young infant because the owner did not desire to care for a child. Further still, lest you begin to think northern slavery lacked violence, I'll direct you to a journal entry from John Josselyn's 1674 Two Voyages to New England:
... the Second of October, about 9 of the clock in the morning, Mr. Mavericks Negro woman came to my chamber window, and in her own Countrey language and tune sang very loud and shrill, going out to her, she used a great deal of respect toward me, and willingly would have expressed her grief in English; but I apprehended it by her countenance and deportment, whereupon I repaired to my host, to learn of him the cause, and resolved to intreat him in her behalf, for that I understood before, that she had been a Queen in her own Countrey, and observed a very humble and dutiful garb used towards her by another Negro who was her maid. Mr. Maverick was desirous to have a breed of Negroes, and therefore seeing she would not yield by perswasions to company with a Negro young man he had in his house; he commanded him will'd she nill'd she to go to bed to her, which was no sooner done but she kickt him out again, this she took in high disdain beyond her slavery, and this was the cause of her grief.
You were still, for first generation enslaved, taken from your homes, marched to the coast, packed into prisons, and there jostled, fondled, and inspected before being loaded on slave ships for a voyage that could last weeks or months as they filled the ship at other slaver forts. Conditions were miserable and disease ridden, cramped unsanitary conditions, rape, and death were a reality. In some cases, such as the Brig Polly in 1806, the mortality rate was in excess of 50% - Polly dosembarked 33 enslaved Africans out of a cargo of 129. In order to stave off disease for the crew and valuble slave cargo those suspected of infection would be quarantined, in the 1789 voyage of the DeWolf ship Polly (unclear if same vessel) this culminated with an enslaved women with smallpox being hurled overboard, still bound to the chair they had bound and hoisted her to the top of the main mast in 3 days earlier. She was alive at the time.
If you are more impacted by imagery than words, which I do think makes the barbarity of slavery stick more, I'll offer up my preferred photo to drive the point home : Gordon, during medical examination after escaping to Union forces in Louisianna during the Civil War Smithsonian Collection.
There are a number of reliable accounts, the most accessible being the the Library of Congress collection of former slave narratives which was collected in the 1930s.
Ultimately you cannot exaggerate or play down the fact that slavery existed; that it was harsh, demeaning, and played a major role in subjugating a racial minority within the United States. To think that racial rhetoric that drove that subjugation has entirely expired is fallacy. To that end, if possible I do highly suggest visitong the new Smithsonian Museum of African-American History and Culture to learn more.
