Will pushing my lower jar forward, destroy the purpose of Elastic Bands?

I have a Class 2 Overbite, which makes my chin look "weak" and what I tend to do is push my lower jaw forward to make it look more "normal". I've had braces for 6 months, and I was told I am getting Elastic Rubber Bands after 2 years of Braces. Will pushing the jaw forward while having the Elastic Bands, destroy its purpose? Since it is supposed to bring the lower teeth forward to meet the upper teeth.

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