It states in this week's parashah (Bereishis 25:8), ושבע זקן טובה בשיבה אברהם וימת ויגוע, "And Avraham was niftar at a good old age, old and satisfied." The Siforno translates ושבע as "He was satisfied with everything he desired to see and to do in his lifetime." This isn't a simple level. Few people are happy with their lot.
The Rabbeinu b'Chaya elaborates: “This pasuk teaches us about Avraham's good middos. He left this world fulfilled. He didn’t need more. This was also Dovid HaMelech's level, as it states (Tehillim 21:3), לו נתתה לבו תאות, 'You have granted him his heart's desire.' Dovid had everything he wanted, he didn’t want more. This is unlike most people about whom it states (Koheles 5:9), כסף ישבע לא כסף אוהב, 'one who desires money will never have enough money.’ Chazal (Koheles Rabba 1:32) say, 'When a person leaves the world, he hasn’t attained half of his desires. If he had one hundred, he wanted two hundred. If he had two hundred, he wanted four hundred.'" But Avraham was ימים ושבע זקן satisfied with his lot. He didn't lack anything. He was happy with what he had.
Another source of Avraham's praiseworthy outlook on life is the pasuk (24:1) בכל אברהם את ברך 'וה, "And Hashem blessed Avraham with everything." He felt he had everything he needed and lacked nothing.
Sarah Imeinu also had this nature of always being happy with her lot. Rashi (23:1) writes, לטובה שוין כולן, all of Sarah's life was good. She was always satisfied with her portion.
One year, on Shabbos parashas Chayei Sarah, the Yesod HaAvodah zt'l (Slonim), couldn't stop speaking about this Rashi. He shouted, געווען גוט שטענדיג איר איז'ס, "Life was always good for Sarah!" This is because she focused on what she had and not on what she lacked, and she always felt that she had everything she needed.
The Chida (P’nei Dovid) writes that the first word of the parashah, ויהיו, can be read backward and forwards to imply that even when Sarah's days were backward and filled with difficulties, she considered them good days- לטובה שוין כולן, "All of Sarah's years were equally good."
