First off, I would caution anyone about doing positive affirmations, or even forced journaling exercises (e.g. gratitude journaling). These exercises are incongruent with how one see's oneself; people who are already grateful or have health self-esteem don't need to do these exercises, and those don't have them and are trying to force it on themselves only see it as a lie (subconsciously). You can't really lie to yourself and will it into existence, and it usually only serves to point out the gap between where you feel you are (e.g. low self-esteem, bad, etc) and where you want to be. That's a hard way to start.

A better place to start is to understand how your undesired behaviors ("bad habits") are serving a purpose for you, and then through that awareness build a substitute habit or coping strategy. For example, you don't have a "video game addiction"; you have a coping strategy that worked well to buffet you against the pangs of failure as you struggled in high school. The reason failure hurt so much is that your parents only conditionally showed affection toward you based on your academic success, so you never learned how to unconditionally love yourself. As an adult with a job and a family, this coping strategy is maladaptive, but is the "best" way you subconsciously feel you can deal with the feelings that continue to well up.

Two books are How We Change [0] and Adult Children of Emotionally Immature Parents [1], although I'd recommend the former book much more to start with.

Side note: if you're picking books to read, make sure to avoid books with a big photo of the author on the cover. That's almost a sure sign of a useless personal growth book.

[0] https://www.harpercollins.com/products/how-we-change-ross-el...

[1] https://www.goodreads.com/book/show/23129659-adult-children-...