In genres like mystery and fantasy that big and difficult thing might mean a perilous quest (slaying the dragon, catching the bad guy, destroying a ring atop a rather unpleasant mountain), for genres like romance and literary fiction that might mean a perilous inner journey (navigating forces outside of one’s control, getting an attractive individual to kiss you, getting over one’s self). Or some combination of all of these.
Often authors will approach novels knowing the protagonist needs to get going on their big quest and start tackling those really difficult things. There’s just one problem: the authors sometimes forget there might be a much easier solution staring the protagonist in the face.
Why would your protagonist risk life and limb scaling a massive building with their bare hands when they haven’t even checked if the front door is unlocked?