This depends on several factors such as:
- Age
- 2nd language acquisition
- Amount of language exposure
- Time and focus spent on pronunciation
A major factor is age. The younger a person is, the easier it is to modify or change one's accent. Someone who is twelve years old and younger will be able to adapt his/her pronunciation to the second language much easier than an adult. The older a person is, the less likely it will be to sound like a native speaker of that language. That being said, there are those individuals who have a talent for language and pronunciation. Then there are others who are able to invest their time to focus and immerse themselves in speech practice. Actors/actresses are good examples of this.
However, the key is to make realistic goals for yourself. Where do you want to begin focusing your pronunciation? At work? At school? Over the phone? In casual conversations? While out shopping? At home? Choose where and how you want to start modifying your pronunciation. The goal should not be to completely "get rid" of your accent, but to enhance your pronunciation within a range clarity that is understood.