Someone told me to be thankful for each one that comes up, goes out in any which way, because it is one less in my body. I guess that's an excellent way to look at it!
The facts may be more 'striking' than this nice way of looking at it. When it comes to infestations, one coming out usually means that many more are in, often thousands. I say this not to scare you but to help you be aware that being content is rarely acceptable when dealing with these things.