Never make it too easy or obvious for your character to get what s/he wants. The more obstacles you place in their way, the more interesting and suspenseful the story. When you don’t know what will happen, chances are your reader won’t either.

Sometimes when things seem to be going too well, it can actually add suspense, at least for a while, because the readers will anticipate things are going to crash. A classic example I can think of for this is the TV show, Scorpion. What always starts out as what they expect will be a simple job inevitably turns into the worst-case scenario. This is what builds suspense and makes the story more interesting. It’s also the way that life seems to work.