My good friend, Carla Neggers, says of plotting, that you create a character, then you put them in a big hole and throw dirt in on them. Every time they try to climb out (temporary triumph), you throw more dirt (obstacles), until the arrival of what many people call the "black moment" and Carla calls the "big gloom" when it appears that there is no happy solution. It's a hard fact, but true, that what's bad for the protagonist is good for the story. Without obstacles, there IS no story.
This is hard for all writers. We create our characters and in many ways they are a part of us. It's hard to throw dirt. We want to make everything right for them. I had a student once who wrote a story where the heroine was tied to the railroad tracks -- a suspenseful, if trite plot turn. The hero was riding to the rescue. The train was coming. The heroine was screaming. And the train ran out of coal and lost it's head of steam. Then the hero came to the rescue. When I asked my student why she had the train run out of coal, she said, "Well, I didn't want it to run over her, in case he didn't get there in time." But it is the possibility that he won't that keeps the reader on the edge-of-the-chair, to coin a cliché.