Think about it, Riley.
If you eat too much celery to the exclusion of other foods, what's going to happen? You're going to eventually show serious medical problems. Celery has very little nutritional value, and in fact takes more calories to process it than it provides.
But, let's restrict this to simply protein sources...
Beef, lamb, pork, poultry, fish? Some are healthier than othes, but eating too much animal protein has myriad problems associated with it, from cholesterol to toxic chemicals such as PCBs to mercury.
Pulses other than soybeans? Incomplete complex proteins, with some indications that overdosing on these can cause metabolic and liver problems.
Eggs, cheeses, and other animal derived sources? See meat above.
Nuts/peanuts? Other than the allergy issues, which are crucially important for some people, nuts are a pretty excellent source of protein.
Once again, moderation is the key to the consumption of any food, and the maintenance of any healthy diet.