Hey.

I used to be like this. I believe I am not that way, anymore.

TL;DR:

• understand why
• keep a routine designed to help you grow as a person
  • meditate
  • exercise
  • work on yourself every day

First off, are you sure you don't want to be like that?

There's all kinds of people in this world, no-one but yourself should determine what kind of person you want to be.
The key thing is this has to be a self-imposed change, not "because of what people think" — otherwise, you'll find yourself going back to current status soon enough.

In my case, I've come to understood my actions where a reflection of a lot of bottled up stuff from a couple of sad stories in my past. I looked into myself and decided "enough is enough".

Know yourself

What is it that you really want in life? Who do you want to be, in the few years we have in this life?

The goal is to understand why you are acting in a way you don't consciously accept as good behaviour on your part.

As /u/ortofon88 suggested, meditation is a great way to get to know yourself.
Regular practice beats long sessions, I recommend something like 20min every weekday and a longer (1h?) session on the weekend.

A few places to look:

• /r/Mindfulness
• /r/Meditation (wiki)
• Mindfulness in Plain English: a great introductory book
• When Things Fall Apart: this helped me immensely. The audiobook read by the author is great.
• Calm.com: what I use for guided meditation on daily basis

What is a better version of yourself?

Actually take the time to find out what a "perfect" you would look like — the goal here is not to become perfect, but to identify the main goals you want to accomplish in life.

Grab a notebook and a pen, go down to your favorite coffee shop/tea house/beach. Sit down, grab something to drink. Put your headphones on and get some music playing. Now, write whatever comes to mind for an hour or two.
Keep this question in mind: what is my legacy to the world and those around me?

Work on being you

Get your act together on the path you choose, not whatever wants spring into life on a day-to-day basis.

Routine is a must: keeping a routine designed to push you to your goals is the best way to actually keep you on track. Personal motto: "no zero days :)".

A few resources:

• Exercise: it helps clear the head and keep you healthy. /r/Fitness & /r/running
• Routine: /r/theXeffect

Finally, the most important lesson: the world doesn't end tomorrow, but today will set a path for tomorrow!
Nobody's perfect and life has a way of messing things up. You just keep doing you, one step at a time.

Never let anything stop you from taking a step every day.

Feel free to PM me.

Hope this helps.