If you want to totally screw up your life, here's my advice: cultivate some bad habits. That's how most people do it. Very few people screw up their lives by drinking once, but a lot of people screw it up by developing a drinking problem. I've never heard a story of someone who went to Vegas for the first time and lost his entire fortune, but I've heard plenty of stories of people with gambling addictions who have blackjacked their way to bankruptcy. Even breakups are far more likely to be caused by habitual bad behaviour than by a single action (even in the case of cheating, a lot of couples stay together).
This is because a single action doesn't have all that much leverage on your life. But habits, on the other hand, define us as people-- literally. What we do regularly becomes a label. Bob's an alcoholic. Tom is a cheater. Raymond is a gambler. Habits change ephemeral verbs (Tom cheated) to nouns. Once you're defined by your habits, it takes a lot to change that. If Bob doesn't drink for a night, he isn't magically changed into tee-totaler. You are your habits.
And that's why habits are my religion. I write about them all the time, from every single angle, and that's mostly a result of being fixated on habits in my own life. If you can change your habits, you can change who you are. So I pay very little attention to rare occurrences and work on my habits constantly.
The cool thing about changing habits is that it's very efficient. It's like the difference between cutting down a tree by axing the trunk, versus trying to pick every single leaf, then twig, then branch, then peeling the bark, and then finally getting to the trunk. Just cut down the trunk and the whole tree is gone. Trying to control a single occurrence without identifying and working on the habit is like picking a single leaf. It's easier than chopping down the trunk, but it doesn't really change anything.
For example, in the past couple weeks in Japan I ate three meals that aren't on my diet. Ramen twice, and a couple pieces of sushi. No big deal. My habit is to eat extremely healthy and that has become part of my identity to the point where healthy food is what I actually crave. In the past year or so I've been slacking on running and working out. When I was in Tokyo I ran a few times, but that doesn't mean I'm a runner. These are just leaves on the tree. Add a leaf or take one off, and it's still a tree.
This is also how I think of health, by the way. I live a healthy lifestyle (good food, fairly active, no stress, lots of happiness and good friends, good sleep, etc) and a result I never have any symptoms (leaves) to treat. I've never swallowed a pill and can't remember the last time I was sick.
This is a pretty easy way to really take control of your life. You will make billions of decisions and actions in your life. It's not realistic to think that you will evaluate each one properly and make the right decision. Even if you could, you probably wouldn't want to; that's a lot of stress. But instilling a few good habits, which then make decisions on autopilot, is pretty easy. Set up good eating habits, and almost all decisions about food go away. Learn good social habits, and a lot of problems with other people go away. Develop good work habits and your career ends up being manageable. It's sort of like having an entire staff (your subconscious habits), rather than trying to run a factory by yourself.
Yet another amazing thing about habits (and, yes, I realize I'm starting to sound a bit like an informercial) is that they become more and more easy to maintain as time passes. When you plant a seed you have to protect it and water it and feed it. Once it becomes a tree, you can leave it alone and it will continue to deepen its roots without any attention from you at all. The same goes for developing habits: at first you have to be hyper vigilant and make sure the habit never gets broken. After a while it fades to the background and becomes integrated with your identity.
So if you have a problem in your life, rather than solve the problem, try to look at why that problem exists, and if you dig deep enough you'll probably find that the problem is rooted in a habit. Can't find a job? It's not because your industry is in the dump or because you don't have the right suit-- it's because you don't have a habit of over-delivering and producing excellence. Or maybe it's because you aren't in the habit of networking with people in your industry. Or even if it isn't BECAUSE of any of these habits individually, any one of them could solve the problem forever AND produce side benefits that you aren't expecting. That's the effective and long-term way to solve problems, and it's the only self improvement strategy with legs.
I love habits. You should too.