Just when you want to start believing again, the Trail Blazers betray you. Just when you allow yourself to imagine the possibilities of a monumental late-season rally, they break your heart. Just when you convince yourself the playoffs aren’t just a foolish dream, they make you curse under your breath. After providing a jolt of hope with back-to-back road victories, the Blazers ended their make-or-break five-game trip with a whimper Sunday night, losing 103-83 to the Oklahoma City Thunder before 18,203 at Chesapeake Energy Arena. The game — and the just-completed trip — were a microcosm for this sometimes-promising, sometimes-depressing season. The Blazers have teased and tantalized with their potential most of the season. But in the end, they seem destined to disappoint. “It’s just how the season has gone,” Wesley Matthews said. “And it’s frustrating. It’s frustrating, it’s irritating. But at the same time, there’s so much promise. We’re just not quite there.” The Blazers (33-37) were right there for 3 1/2 quarters Sunday night against a Thunder team that is a legitimate challenger for the NBA Championship. When LaMarcus Aldridge hit a 19-foot jumper with 6:00 left in the game, the Thunder held a precarious 88-83 lead and it looked like the game would go down to the wire. But in a scene that has played out time and time again during Portland’s visits to Oklahoma City, the Thunder proved to be too dominant down the stretch.