One element of the Fiscal Cliff explained here. This one LIKELY will affect your paycheck in January. Ouch!

One element of the "fiscal cliff" that just about all wage earners, regardless of income, are affected by is the 2 percentage point DECREASE in the Social Security tax that workers have enjoyed since 2010.  (You didn't know you had a tax cut??) .  It is currently at 4.2% from its "normal" longstanding 6.2%.  The tax is applied on your gross pay (wage X hours worked. Or from your salary if you are a salaried worker).

This temporary reduction was implemented as part of a "fiscal stimulus" bill/law. It served as a quick and easy way to get money into the hands of people, and the assumption was that it would likely be spent in the economy and provide a needed jolt for the demand for goods and services.

This reduction seems small for each person, and it is, but in the aggregate it is roughly about $120 billion on an annual basis injected into the economy.

Because it amounts to so little per person the economic thinking is people wont notice it, hence will be more likely to spend it than to give it much thought about saving it.  This is not entirely true for all people, but it does seem a very likely outcome.

The trade-off from this particular tax cut is that the $120 billion is supposed to pay Social Security benefits for current recipients.  Those benefits are going to be paid regardless.  This will necessitate borrowing to compensate for the tax cut.

There is no such thing as a free lunch.

The consensus right now seems to be this tax cut will expire and go back to 6.2%.  But, as with all things political, we will have to wait and see.