Winter of 1776/77 saw a continuation of hardships. The weather on many days was very cold and George Washington's troops started to suffer from the elements and the constant flight from the British.
The provisions started to run low for both armies and morale became a problem as the shoes started to be worn bare and the soldiers left bloody footprints in the snow during their forced marches.
Several things did however start to work in the Americans favor though.
Popular support for the rebel cause started to increase as the British ran low on supplies and started aggressive 'foraging' of the residents' belongings to supply their army with food for the men and hay for their horses. The fact that some loyalists had their food supplies foraged started to erode support for the British even in Tory households.
Under George Washington's leadership - the underdog army of the Americans made a couple amazing attacks on the Hessian forces stationed across the frozen Delaware river. Washington actually crossed the Delaware River twice in horrible conditions, once during a Nor'easter and fought the ice flows to bring a minimal force to attack the unsuspecting Hessian legions. The element of surprise helped the small force of hungry and tired Americans route the German Hessians from their defensive positrons.
The Americans conducted constant guerrilla raids against the encamped British causing them to stay on constant alert with clothes on and bags packed. This constant threat of assassination diminished the morale and effectiveness of the British army. (I don't even need to make modern day comparisons- we can figure this one out)
There was also a successful attack on Trenton, NJ which drove the garrison of British from their fortifications.
The combination of increasing morale of the American army from the string of victories, perceived feeling of fighting for their country, strategy of attacks on vulnerable British positions, interruption of the British supply chains and the fatigue of the British army which was constantly under threat of attack started to turn the tide of war in Washington's favor.