"Today some actors get a little full of themselves about what they're doing"

This quote by Ray Liotta is referring to the reality that some actors can become excessively confident in their abilities and start to think that they are better than they really are. This can result in them becoming conceited and believing that they are above everyone else. This can be harming to their career as it can lead to them not taking criticism well and not being open to useful feedback. It can also result in them not taking their task seriously and not putting in the effort that is needed to be effective. This can be a substantial detriment to their profession and can result in them not reaching their full potential. It is essential for actors to remain humble and bear in mind that they are just as good as their last performance.