To progress, you must take steps. To seek enlightenment, you must first acknowledge your imperfection. To admit these faults, you must agree to change them. To make this agreement, you have to accept that your efforts may never be finished, leaving you faulted yet contradictorily pious.
It's more than a chicken-and-egg. It's the crux of the stalled progressive movement. We feel we cannot relinquish one vice without simultaneously renouncing all of them. We will not question another's splurging while we continue to indulge ourselves.
Example: It is easier for us to nod in agreement with the new Hummer owner rather than point out its ridiculousness only to be caught hypocritically driving our X5. But, more importantly, we refuse to abandon our own luxury item because it sets us on a course that may well be indefinite and frustrating.
Although the sacrificing of wealth in itself can be painful, it is the thought of failing that halts us. To be sure, at any point in this endeavor, you will be susceptible to claims you are contradicting yourself. Unless, you are capable of walking away from all things material at once, you may be considered flouting your own tenet.
The questions will come in both friendly banter and personal attack. Why do you still have X? If you're so damn good, why haven't you achieved Y? Why should I listen to you when you haven't taken care of Z?
Your guttural response will be to lash out at your friends' own weaknesses, vices. It is only natural to attempt to regain respect by pointing out your moral superiority. But it's not productive. You will merely come off as even more self-righteous than your friend had originally suspected.
Sacrifice implies humility. Suck it up and explain that you never claimed to be perfect and acknowledge you are far from it. It's the truth. If it helps, try to understand where your friend is coming from. Your simple pronouncement of change is indeed viewed as a challenge to him. If you are diverging from a path he still respects, adheres to, even if you consider it small potatoes, he cannot help but feel persecuted, cast as wrong.
This is why it's imperative to stop preaching, to your friends and otherwise. I know, once you feel you're onto something, you feel compelled to speak it, shout it from... something. But you must avoid the temptation if you are to accomplish what you truly desire, and that is to convince your friend to listen and perhaps give your idea a shot.
If we can avert the onslaught of criticism and justify our position in a rational, non-pedantic way, we're there, buddy. We cannot wait for all ducks to be in a row, stars to be aligned, and nest eggs to be fully conceived to embark on change. To do so is to postpone the inevitable, although perhaps until another, someone else's lifetime. To wait is to stall, for nothing holds you back.