Feeling guilty and the stress that it causes is probably doing you more harm
than the small portion of ice cream once in a while...
Do a search on orthorexia, there is such a thing as eating *too* healthy. ;)

Neither muffins nor ice cream have to contain any trans fats. Well, milk
does contain a small amount of naturally occuring trans fats (CLA), but
they're nowhere as unhealthy as the kind you get from hydrogenated
poly-unsaturated oils. But if you eat reasonnably good quality ice cream or
muffins (home-made, organic, quality producer...), that are not made with
hydrogenated oils, they don't have to be loaded with trans fats. Yes,
they're more expensive. That's the advantage of eating things in small
amounts, you can afford quality...
Balance is something that is achieved on the long term. If 90% of your meals
are healthy, then you have a healthy diet...
Likewise, trans fats are progressive. Just check the statistics between
France and USA on cardio-vascular deaths. Despite a higher cholesterol rate,
we score almost three times less deaths. Yet, the average French still eats
around 2g of trans fats a day (vs 20g for an American)... So, it seems that
2g is low enough to achieve good enough results...
Saturated fats seem less of a problem. Many "successful diets" (i.e., the
ones from countries with low cardio-vascular deaths) mix the three kinds of
fatty acids. Check the Cretian diet for instance, they still eat saturated
fat sources (lamb, cheese, eggs...). If mono-unsaturated is your main source
of fats (like olive oil), adding some saturated and poly-unsaturated fats to
the mix is not going to hurt you.

It's a continuum, so obviously, you won't get a clear cut value, with
healthy on one side and unheatlhy on the other. Just remember that eating
food you like reduces your overall stress level (decrease in cortisol), and
that this is also healthy. It's a balance between how healthy you want to
eat, and how much you want to enjoy eating and what is sustainable long term
without frustration. I'm sure a gruel and pills diet could be made to be
100% healthy, but would you really enjoy eating it?

Don't beat yourself up about having an occasional muffin or a bit of
ice cream.   Instead, intelligently fit these choices into your
overall eating plan.  It's all a matter of degree.  Have some
occasionally if you want, and better yet, plan for it.  From reading
your post, it sounds as if you're trying to get educated and move in
the right direction in regards to lifetime eating habits.  

Ice cream and muffins don't have to contain trans fats.  Educate
yourself; learn to prepare some of your own food if you can't find
suitable commercial alternatives.  Google is your friend.

You're really going to have to make that decision for yourself.  No
one is going to be able to tell you X times that you can have muffins
or such.

Who told you that eating properly has anithing to do with limiting carbs?
Last time I checked carb foods like peaches, millet, lentils and others
where all linked with less cancer and less stroke risk, favorable
micronutrient intake and improved glucose tolerance and tryglicerides
Now, if you mean refined carbs, you're right, but please call things
with their proper names
What happened to the difference between refined junk carbs and healthy
unrefined high carb foods?
If we don't want to create confusion we should find another names for
high carbs refined foods as they're not carb anymore, poisons I'd say

I don't think isolated rare episodes of bad foods eating are so important
What is most important in nutrition is the larger pictures and your
overall diet, if you don't feel sick after eating a muffing few times a
week you shouldn't feel guilty either

To me a good rule of thumb is that your diet should be 90/95 unrefined
and healthy
If the other 10 to 5% of your diet is less healthy I don't think you'll
notice much difference, 5% of unhealthy foods is not enough to have an
impact on your body when this little amount is couteracted by all the
healthy phytochemicals and urefined foods you consume
If you feel to much guilty you can still find "healthier" alterative to
your junk foods: whole flour muffins, no sugar icecream

Daniel