If you or someone you care about has allergies, then sleeping with your pet may not be an option. People who suffer from asthma or allergies will have trouble breathing and sleeping if they sleep with their pet. In other cases pets can also interrupt sleep with their movements and noises. They can disturb you with their nighttime scratching, licking, and other typical pet behavior. Also, keep in mind once you allow your pet into your bed, it will become used to it. As we all know old habits are hard to break so if it comes to a point where you need to prevent the pet from sleeping with you, it could become aggressive and display abnormal behavior. Many owners let puppies or small pets sleep in their bed while bigger pets remain on the floor in the room for comfort. Growing up I used to pet sit two Dobermans and they preferred to sleep in the bed. In many ways the warmth and comfort helped me sleep, but in other ways like when one would move around, you do get a paw to the face on occasion. While it may or not hurt, you love your pet and sleeping with it is entirely up to you.
All other issues notwithstanding, the most important thing you should know about sleeping with your pet is that it comes down to personal preference. Your animal loves you and more than anything it just wants to spend time with you and sleeping is a good, uninterrupted way of doing it. If you want to sleep with your pet, then do it. If not because of personal and health reasons, then so be it. Even though there are plenty of things one should know about sleeping with pets, there is no definitive reason as to why or why not. Your pet is personal to you and not one single pet is exactly like another so you shouldn’t have to defend sleeping with your pet or not. Of course there are exceptions, but if you want your pet on the bed, no one can stop you, so just go for it and spend time with your pet.