You need the best "you" to show up when it counts
The first thing to accept is that there is not one 'you' - there are multiple 'you's, eg you at work, you at home, you on a good day, you on a bad day, etc. It's important the right 'you' shows up in any particular situation - especially important when that situation is challenging.
It helps to be clear about your strengths, so find an image for your 'best self' that instantly brings these strengths to mind. My 'Labrador Dog with Glasses' instantly reminds me - with a smile - that I am 'Friendly, Reassuring, and Insightful'. The smile switches the limbic to positive.
Try these GREAT practices to cultivate a more positive 'default' mindset. Also, don't forget the importance of sleep - the tired brain is more likely to make negative associations than positive ones. Read 'Why we sleep' by Dr Matthew Walker or 'Life Time' by Dr Russell Foster.
It's also important to remember that our personality is NOT all we are. Our personality simply represents the habitual patterns of limbic response formed in our early years as a way of dealing with the world's many perceived threats - the 'stuff that happens'. Development is not only about using your personality well, but also using your PFC to access what Jung called your bigger SELF. This is often where we discover our true purpose and access our full potential.