It may surprise you to hear it, but it isn't just the people who get laid off who feel like crap. Of course the remaining people are going to be sad that their friends have been fired and they may feel anger at the boss and the company. And they may also feel anxiety over their own job security, since it's clear that the company is having problems and layoffs are one of the solutions. Sometimes the people who get to keep their jobs suffer from what's called 'survivor guilt'.
Even if someone is relieved to still have a job, they may feel guilty about feeling relieved. They know how tough it is to find a job and they are glad they aren't the unemployed one, but they feel some remorse about feeling good. And the decisions about who stays and who goes can be complicated - and not always based on merit. A survivor with low self-esteem may feel that other, more-worthy (or more needy) people got fired and might feel guilty about staying.
Another thing you might feel is overworked. Unless the business really is shrinking, after a layoff there is going to be more work for the people who are left. You may be grateful that you still have a job, but you'll have to balance the priorities of the workload with the realities of how much you can accomplish.
As a survivor, I think you should try to stay in contact with those who got fired. It may be awkward at first, but you'll have to judge whether the communication is desired or not. It's such a traumatic experience to be fired and people will respond in different ways. Certainly, if your fired friends want to meet you for lunch, you should go. Listen patiently if they vent, but don't let them make you feel guilty for staying. It wasn't your decision.
The most advanced companies today recognize survivor guilt and anxiety and workload and try to do something about it. You boss should talk to you about your value to the company, what the company strategy is, and how the work is going to be distributed among the remaining employees. If you have questions that aren't being answered, take them to your boss. Unclear or evasive answers are signs that this may not be the last downsizing.
