What you choose to think about matters.
Your reticular activating system seeks out what it thinks the brain wants and filters out everything else.
In other words, what you focus on is what your brain will try to find. Your brain doesn’t distinguish between whether you are focusing on it for positive reasons or negative reasons.
If you have resentment or bitterness, your brain will try to find experiences that match that focus and filter out everything else. Everything else includes potential opportunities.
Let the resentment go and focus on the good and positive you want in life. This approach will maximize those opportunities. As a side benefit, it will cause your RAS to filter out the negative experiences that you resented or were bitter about.