What prevents everyday objects from reacting?
As I see it, two factors: thermodynamics and kinetics. 

Thermodynamics: Many of the reactions that "don't happen" in everyday life are not favored thermodynamically, we call them non-spontaneous. This means that the products would be higher in energy than the reactants. Such reactions can certainly occur if you supply external energy (charging your cell phone battery, for instance, is a non-spontaneous process). But, without applied energy, non-spontaneous processes generally will not occur. Reactions that we observe in nature are generally spontaneous, favored by thermodynamics (with lower-energy products). Some thermodynamically spontaneous  processes are not observed to occur, even when we might naively expected them to. Example: Sugars decomposing to $CO_2$ and water is a very energetically favorable reaction, in fact the energy released from this process fuels nearly all known life. However, we do not observe our table sugar decomposing in its container because without outside help like enzymes and applied heat, the process is terribly slow kinetically.

Kinetics: For us to observe a reaction happening, it must proceed at rate that is fast relative to our human scale of time. Perhaps your fingers fusing to your keyboard is thermodynamically favored/spontaneous, but if it takes hundreds of years to occur then for our human purposes we may regard it as "no reaction". Indeed, the decomposition of most types of the biomolecules constituting our bodies is favored thermodynamically, but the kinetics are so slow (440 years for table sugar)°. There are a few ways to increase the rate at which a reaction occurs. To occur, a reaction requires a certain amount of activation energy. Think of this as hill you have to climb before you can sled down to the products (or up, potentially). The reaction does not occur if the starting material molecules do not possess enough energy to climb the activation energy barrier. You may help them overcome the barrier by supplying heat; thus, heating your table sugar will allow it to decompose into $CO_2$ and water before your eyes (the water will be released as steam of course). The other main way to increase the kinetics of the reaction is to lower the hill, instead of adding the energy to climb it. That is, use a catalyst like an enzyme to lower the activation energy barrier of the reaction. Without such external factors like applied heat and use of a catalyst, many reactions that are thermodynamically favored will be disfavored by kinetics, and not proceed at an observables rate. 

So the reason the universe isn't a useless, constantly rearranging chemical soup boils down to thermodynamics and kinetics. Even if a process is thermodynamically spontaneous, it may be kinetically slow. I should point out that in a lot of places, such as the centers of stars, there is indeed a copious abundance of uncontrollable chemical and nuclear reactions. And planets like Jupiter pretty much are a useless chemical soup (no offense to Jupiterians). But in our favorite places on Earth, at room temperature and atmospheric pressure, the carbon in our bodies isn't going to undergo nuclear fission and become lead (thankfully).

By the way, this is in not a silly question. In fact, if a chemistry student doesn't wonder this, one may question if they are actually learning the subject. I applaud you for your curiosity.