You have made the transition to a primal lifestyle, you are feeling great and heading towards your goal. You are enjoying the food and learning new kitchen skills all the time.
However there is just this nagging little voice in your head that says "have the sandwich, go on it's only one cake", so the question of "shall I cheat" comes in.
Now this does link in nicely with the 80/20 rule so go back and read my previous post It goes into what 80/20 is and how to use it, but before you do, consider these things first.
Are you still trying to get to your goals and do you want to reach them in the quickest and most efficient way? If yes then a cheat is probably not the best thing to be doing. Any thing off plan is going to hold you back to some extent, so if you do cheat enjoy it but don't be to disheartened when your weight doesn't shift the right way and your digestive issues return.
Brings me nicely to the next point, is it worth it? If you know that you have an intolerance to something that gives you undesirable effects is it really worth feeling ill? It could re-induce IBS, heartburn, bloating and skin flare ups. The cheat is usually never as good as you imagine it to be, the takeaway may give you a moment's pleasure but could much longer term problems.
How long have you been on this lifestyle? If you have been doing this for a while, your little slip up will probably not have as much as an issue as someone who has been doing it for months. At the start you are trying to reset the body, giving it time to readjust to a more natural state. You are trying to break your bad habits and change your taste buds to real food. Having a cheat of any kind at the early stages can easily rekindle your desire for something that you have been trying to avoid. That said even if you have been doing it longer term it's not a licence to indulge all the time, it would be a slippery slope to your old ways.
Think why you started in the first place were you trying to break bad habits? If yes remember a habit is something that is hard to break, is having one cigarette a week better than one everyday? Probably but it's not going to help you fully break the habit. The same thing will happen with food choices and that cheat could start it up again.
With a similar point to my 80/20 rule don't factor in a cheat meal, it shouldn't be a planned "i'm having a cheat on friday". This kind of thought process leads to a reward type of meal, the "I have done well all week so I deserve a treat" mentality. Now this can be of benefit sometimes, having it can remind you of why you don't eat something anymore when your negative issues resurface, but they can also just reinforce an addiction to a certain food that you were close to breaking.
To bring this all together a cheat is probably not a good idea, and I think we all know this deep down. However we do live in the real world of modern indulgences that we know are bad for us, and social events that seem to be there just to throw us off track. However a cheat can sometimes be helpful from a psychological point of view even if it does just remind you of the bad implications.
Try and keep in mind that you are on a long term lifestyle change that will hopefully lead you to a fitter and healthier you, a cheat occasionally probably won't totally throw you off but accept that it isn't going to help you towards your goal and get back to the plan at the next meal time.