Generally, spaying or neutering your pet will not change its personality. If there are any effects on behaviour, they tend to be positive (reducing unwanted behaviour). Spaying or neutering will not change your pet's affection level or playfulness.
For females, there is typically no change at all. For males, there may be a reduction in some aggressive and roaming behaviours. If you have more than one pet, you will find they often get along much better if they are all spayed or neutered.
Learn more about the benefits of spaying and neutering your pet.