Two investing adages might seem to contradict each other. Many investors have long followed the maxim to "buy low and sell high." On the other hand, they've also been told: "Don't try to catch a falling knife."Which of the familiar sayings applies to United Parcel Service (UPS 0.85%)? Shares of the package delivery giant have plunged more than 50% below the high set in 2022. However, I don't view UPS as a "falling knife" to avoid. Instead, I think this ultra-high-yield dividend stock is a great pick for lon ...