I hope you have a chag kasher v'sameach!
So. Pesach is here. Let's assume this is your first or second Pesach (particularly speaking to those of you who haven't converted yet), and that you're trying to "do it all" this year. By now, you've cleaned your home, maybe even kashered stuff. You probably have everything that doesn't move covered in tin foil or contact paper. You're ready, and you're going to make the best Pesach ever!
That's all well and good (and well done!), but don't beat yourself up if you mess up or simply don't make it all of Pesach without chametz. Pesach preparation can be very difficult, and everyone talks about it, but I don't see people talking about how difficult it is to actually do Pesach itself. Everyone says, "Oh, I'm so glad Pesach is here! My house is clean, and now I can relax and have a great week!" While that's usually true for the first night, I don't think that's necessarily true for the other 8 days (or 7 in Israel). Maybe these people who have been doing fast days and making Pesach their whole lives don't think anything about a major (and sudden) diet change, but converts and baalei teshuva often have a very difficult time making such drastic diet shifts, and that difficulty can last several years.
If viewed objectively, Pesach is very similar to a crash diet. You're going cold turkey on almost all carbs that the average American eats. Your diet over the next week will not be balanced, and you will probably be lacking nutrients your body needs. It's hard on your body, and it's hard on you mentally. Forbid a food, and instantly your body is ravaged by cravings for it.
So if you don't make it...acknowledge it, see what you can do to prevent it from happening again, and move on. There's no need to beat yourself up over it. There is certainly no need to feel like a terrible person if you haven't converted because you're not obligated yet. It's voluntary, so there isn't an aveirah.
Pesach can bring out the OCD in you, in addition to the guilt. Don't let Pesach ruin Pesach. Conversion is a process for a reason, just as we all have ebbs and flows in our Judaism. Remember to learn from all your experiences, both the good and the bad.
I hope this little Downer Debbie pep talk ends up being unnecessary for you and that you have a wonderful, relaxing, kosher, delicious, guilt-free, and constipation-free Pesach.