Wow, I have a lot to say about this.
First of all, I know the fear. It's the fear that when you ignore those impulses to go back, to pray, to praise god, that you are 'hardening your heart' and will have only yourself to blame on judgement day.
In some sense, you are hardening your heart. You have to, because being in the cult so long has meant people have stomped on it until it is goopy mush.
But this doesn't mean you are sinful. What you have to remember is that Christianity operates on its own internal logic. By simply thinking "I'm hardening my heart right now", they have already won because you're using their logic.
When they question you or preach to you, they will be coming at you from their inside-the-cult perspective, using their internally consistent logic. You won't be able to debate it because you'll have to work on their assumptions just to have a conversation (eg god is real and is the christian god, jesus gave you a gift, etc). When you work on their assumptions you will naturally sympathise with their logic and their mindset and by their logic, they are right. Bam, you just lost the game. It becomes more possible over time to pick it apart on the fly, but they will consistently derail the conversation and because you are still used to the logic making sense, a newly deconverted person finds it hard not to be swept away by it all over again.
Instead, you have to remember that there are all these holes that appear in that logic when you stand outside looking in, evaluating the structure as a whole. Don't get carried away into arguments that are based on assumptions your debating opponent *hasn't actually proved yet*. Such as, "the Bible can be trusted for reasons other than 'God says so'". Any argument made using this premise, without first proving it, is never going to be valid.
Find those premises when someone makes an elaborate or personal argument, and ask them to prove it first.
Secondly, you actually don't have to argue your own case if you don't want to. You'll feel the need to--but it's your former Christianity defence mechanisms jumping to the fore. When you were a Christian, any non-Christian worldview was a threat to how you made sense of the world, and it had to be destroyed as quickly as possible so you could maintain your peace about how you were right.
Now? You can let other worldviews be. People are allowed to believe what they want. You don't have to correct them, the existence of their beliefs no longer threatens your beliefs. You are in a much more chilled out position than they are.
Remember that your only point is "I don't find the Christian God convincing". They will ask you what you think is better or more convincing -- "I don't know" is fine. Remember, you're not trying to counter-prove anything, not even atheism. Just cause they get all worked up about their case, doesn't mean you need to match them.
They will be assuming that you are coming from another viewpoint that you have to viciously defend in the same way they defend Christianity. When you don't have an opposing viewpoint, they have nothing to cling onto and attack, and it really throws them off!
It is perfectly justifiable to become convinced that a theory is invalid because of its own flaws, and then leave it, all without being convinced that a replacement theory is better. You can exist without a theory.
If they start to get personal, you don't owe them any kind of answer or explanation. "I'm sorry but that's not relevant to why i left and I don't want to answer it because it's too personal" is fine. They no longer own the rights to hearing all your most intimate struggles and emotions. You get to choose who knows about them. If they think that makes your whole argument invalid then what they think about you cannot be your problem.
Thirdly, having said all this, you may find it easier to pick holes in an argument than you think. When you look at people's testimonies with these newfound eyes, you see dozens of other more non-Jesus explanations, including "statistically speaking, coincidences have to happen pretty often!" You may not want to say this to your loved one's face: in this case, a smile and an "I'm glad you derived strength from your faith" will do.
Youtube some personal testimonies as practice, it's likely you'll instantly start spotting holes in them. If not, watch some Atheist Experience vids where they debunk callers.
Also remember that sometimes things in life are weird or unexplainable and creepy. You're going to have to be comfortable with that because life is like that sometimes. I still have things I can't explain--but it doesn't mean that it was the christian god that did it.
There could be a whole world of supernatural ghosts, aliens, vampires, angels and leprechauns out there... but none of that means there has to be a god as well.
Finally (I'm so sorry about the length of this) I politely question the need for a formal "coming out". I don't know if that's what you have in mind--but if you do, may I suggest limiting it to those who directly ask? You can often just stop going to church and tell people "you don't have to go to church to be a christian."
I also encourage you to think about why you are doing this. You may have felt obligated when you were a Christian to" shine your light" and be a witness to the world--but you don't have to live like that anymore. Away from the cult, which likes to make you obligated to be an open book to aid them in controlling you, can develop a sense of personal privacy and boundaries again. You can hide your light under that bushel for all you're worth now. Nobody has to know unless you want them too. They can be as curious as they like but you don't owe them an unsolicited explanation for anything you do.