The challenge is not changing who you are but your habits. We are constructs of our actions. Do you have any particular habits you wish to change? I used to be a lethargic PC gamer who never really socialized, but I changed things slowly (except a crash diet exercise thing I did sophomore year of college.) I also have terrible impulse control at times and have focused on removing the impetus to the problematic situation rather than avoiding the impulse.
There are two ways to change oneself, the cold turkey crash course way (which usually fails) or the gradual habit forming way. I will advocate the latter even though I've done my fair share of the former.
Examples:
I will binge eat junk food no matter what, so I only stock healthy foods in my house. Remove the temptation so you don't waste your self control and concentration on silly things.
If video games are a problem try uninstalling them, packaging up the disks/console and putting them on a high shelf. Making distractions a bit harder to access makes controlling impulses easier.
Pick simple goals, like taking the dog on daily walks the same time every day, will help you build focus and teach you how to schedule your time. Running is also a good habit to get into, just be sure to pick a regular time and stick to it.
You might also wish to pick up cooking meals for your family as that's a good skill to develop.
Focus on building habits. Like waking up early the same time every day, making the bed every morning, putting laundry away, etc