As you are receiving your first paycheck of 2013, the amount may be less than you expected. In 2011 and 2012 the Social Security payroll taxes were reduced from 6.2% to 4.2%. That reduction expired on December 31, 2012.
Here is a post from Dave Ramsey's blog about what the decrease may mean for you. On a salary of $50,000 that is an annual decrease of $1,000 a year or about $40 every two weeks.
$40 may not seem like a lot of money but if you are stretching yourself thin already, that $40 can make a difference. That is why it is important to live on a budget of what you have coming in and going out. If you had figured your budget with the income you have been receiving it is important to rework the budget to reflect the decrease in pay.
It will be beneficial to start living within the budget of what you are actually bringing in, instead of thinking you will eventually catch up. The longer you live beyond your means the more debt you may find yourself in.
It may seem like a decrease in pay, but you probably have been getting more in your checks the past two years than you would have if the payroll taxes had not been reduced.