True story: I’m eating dinner with two old friends. (It’s a downer when you realize “old friends” doesn’t just indicate length of relationship but our respective ages.)

One says, “I hate being fat. I’ve tried everything but can’t lose weight. What do you think?”

“I don’t think you want to lose weight,” I said. (I know, kind of blunt. Normally I would deflect and evade, but I know he wants to hear what I really think.)He raises an eyebrow. “Really.”

“Really,” I say. “If you wanted to lose weight you would. But you’ve chosen not to, and that’s okay. The only problem is you’re beating yourself up for something you choose not to do.”

Why do I think that way? We all know how to lose weight: Eat less calories than you burn and voila! You lose weight. Sure, genetics and metabolism and glandular disorders can make losing weight harder, but the fact remains that everyone who eats fewer calories than they burn loses weight. Losing weight has nothing to do with a breakthrough diet or an innovative workout regimen or somehow flipping a magic fat-burning switch… and everything to do with deciding to eat less calories than you burn.

Losing weight is a choice. So being overweight is a choice too.

Unfortunately other things happen by choice.

“Makes sense,” my other friend says. Then he looks at me. “But if it’s that simple, why aren’t you more successful than you are?”

I winced because I knew where he was going… and because I knew he was right.

“Yeah,” my overweight friend says, eagerly jumping in since the very best table is a table turned. “You’ve chosen not to do better. I’ve heard you speak; you could land bigger gigs. You’ve ghostwritten a bunch of books; you could do more work for high-profile clients. You’ve photographed celebrity weddings; you could do more of those. Don’t tell me you can’t. Clearly, you’ve chosen not to.”

I knew he was right. Not because I’m incredibly talented (far from it) but because success, for any of us, in almost any field, is a decision. I could do bigger speaking events, but my actions show I’ve chosen not to. I easily could land more celebrity weddings if I chased them harder, but I haven’t.

We — definitely me included — often like to think that upbringing or education or circumstances or lack of connections or unlucky breaks hold us back. Thinking that way, if nothing else, feels better because we can shift the blame elsewhere.

But the blame lies squarely within us: The only things truly holding us back are the decisions we make.

If you want to get promoted but haven’t, it’s almost never because your boss is unfair. Instead you decided not to work harder or take more initiative or take on more responsibility… or just play the corporate game the way it has to be played in your organization in order for you to “win.” (You know the “rules,” you’ve just decided not to follow them. Don’t feel bad; I was the same way.) If you want your business to grow but it hasn’t, economic factors are certainly at play but you’ve also probably decided not to change your sales strategy or streamline your operations or just try new things in response to new market conditions. You can see what makes other companies successful but you’ve chosen not to follow their example.

Fortunately, while the blame may lie squarely within us the power lies within us as well. Success is all about decisions — our decisions.

Including deciding what to let go.

Think about your goals. Like most people, yours likely run the gamut: You want to create wonderful relationships, build a family, enjoy professional success, achieve something personal… you have lots of things you want to accomplish.

Great — but there’s a problem. You can’t have it all. And if you choose to try to have it all you will always be, to some degree, unfulfilled.

Say you want to raise a happy family. You can; it just takes effort and attention. Say you want to start a business. You can; you just have to work really hard. Say you want to write a book. You can; you just have to write, hour after hour and day after day, for however long it takes. Say you want to run a marathon. You can, as long as you do the training necessary.

But say you want to do all of the above — and all at the same time. Realistically that doesn’t work. Something will give. Your family needs you more than your running shoes, so training for a marathon will quickly hit the back burner. Your business needs you more than the publishing world, so after six months your book will look more like a pamphlet.

And that’s okay. We can’t do everything, but we can all do a few things really well. Decide what is most important to you, decide to focus on those things… and decide to let go of the things you may want to do but realistically cannot, at least for now.

Me? I can’t be an acclaimed speaker and ghostwrite Obama’s memoirs and photograph the next wedding that hits the cover of Us Weekly. The fields are too disparate and the effort and networking and positioning required to reach and stay at the top in each field are too high. But I feel confident I could consistently achieve one of those goals — if I decided to.

And so can you, in whatever field or pursuit you choose, because your decisions can either make success impossible… or inevitable.

The cool thing is, you get to decide which.

Jeff Haden learned much of what he knows about management as he worked his way up the printing business from forklift driver to manager of a 250-employee book plant. Everything else he knows, he has picked up from ghostwriting books for some of the smartest CEOs he knows in business. He has written more than 30 non-fiction books, including four Business and Investing titles that reached #1 on Amazon’s bestseller list. He’d tell you which ones, but then he’d have to kill you.