What does it mean “to budget”?

I’m constantly keeping tabs on what I spend. Whenever I’m on travel, I give myself a budget range and compete with myself to see if I can come in well below expectations.

I’m interested in the process of budgeting in regards to what it says about a person, our ability to make decisions, how forward thinking we can (or should) be and whether or not this insight should be a practice or a framework. 

What does it it mean to you?