Through the incredible complexity of the coagulation system, our blood clots when we need it to do so, to just the right amount. Something instigates the clottiing. Then just the right amount of platelet action is triggered to start just the right amount & pace of the coagulation cascade to form the clot. And this is balanced by just the right amount and pace of halting and smoothing (lysis, thrombolytic effect) of the clot & injured area back to normally smoothsurfaces in a normal period of due time. The below factors tend to feed & impact on each other & sometimes with more than simple additive effect (may be a multiplier effect).