New thoughts

Doing this month’s homework, I have identified the core thoughts I have had since my childhood that are very problematic and deep rooted in me, generating feelings of anxiety or fear, and bad results in my relationships. Here are the thoughts and the replacing thoughts I think I want to practice :
– I have done something bad > I am worthy whatever I do, I have done difficult things and always find solutions
– People may be dangerous > I like talking normally to people
– I don’t have the right to defend myself > Whatever the circumstance, I’ll protect my family and myself

Could you tell me how can I practise these thoughts so that they become automatic? Do I have to practice different thoughts to check which are the best for me ? What do I do if the old ones remain stronger ?

Thank you