One of the biggest myths about meat is that the liquid in the package that looks like blood is actually not blood.
It is natural that you'd suppose the liquid at the bottom of a meat package is blood since it resembles blood, contains raw meat as you'd expect blood to, and may even have a faint bloody smell. Yet, this is one of those few instances where our use of deductive reasoning fails us; simply because something looks, hops, and kicks like a kangaroo does not mean that it is a duck or kangaroo.
Actually, that fluid that resembles blood is what scientists refer to as "purge"—a mixture of water and meat proteins that drain from the flesh. Myoglobin, one of those proteins, is what gives the water its red or dark pink colour (the same protein is responsible for the reddish pink colouring of the meat itself). Although myoglobin resembles haemoglobin, the protein that gives blood its colour, blood is not what it is.
Meat is approximately 75% water, which accounts for the juiciness of cooked meats. For the purpose of comparison, an adult human male contains about 60% water, while an adult human female contains about 55%. Due to water evaporation during cooking, your cooked steak will always be smaller than what you first placed on the grill.
Therefore, the proteins in meat act as sponges to absorb the water. The proteins in the flesh gradually lose their capacity to hold onto that water as it matures, is handled, or is cut, and when that water is released, the myoglobin floats out with it.
The age of the animal when it was collected has a major impact on the colour of the "purge." Younger animals that have been harvested have less myoglobin than older ones. The purge packaged with pork is primarily pink, whereas the purge packaged with steak is a darker red because pigs are typically harvested at a younger age than cows.
A rare steak will leak red juices, whereas a well-done steak will have clearer juices because myoglobin changes colour when it is cooked.
Remember to use caution when handling "purge" even though it could be comforting to know you aren't handling cow's blood when you open your boxed steak, it is rather disheartening if you're a vampire.
You should still wash your hands after touching it in an attempt to keep it contained to prevent cross-contamination; you might want to wait before eating it until it has reached the right temperature because it may carry the same pathogens as raw meat.
At any rate, better safe than sorry. Other than that, enjoy your scrumptious steak.