I was wondering if excitement is also bad for your body. I know it uses the same parts of the brain. And when i feel excited I don't want to eat and i get jittery. it is also the same with stress or anxiety.
Stress and excitement both activate the sympathetic nervous system, so they can feel very physically similar (high heart rates, etc.) The main difference is in higher-level brain processing, where stress is subjectively perceived as negative and excitement as positive. Interestingly, there is a study that proposes "anxiety reappraisal" in which you tell yourself you're excited instead of nervous, to facilitate management of high-stress situations. See popular press coverage here: http://nymag.com/scienceofus/2016/03/youre-excited-not-nervous-you-just-keep-telling-yourself-that.html and the original study by Alison Wood Brooks here: https://adobe99u.files.wordpress.com/2015/06/xge-a0035325.pdf
Although you do activate a lot of the same systems in both cases, I would think your biggest difference will be what else you activate when excited, which would be Dopamine, Oxytocin, Serotonin, Endorphins, etc. When you are stressed you will actually release cortisol which will inhibit excretion of other feel good chemicals. You may release the feel good ones when the stress has passed, depending on the type of stress (horrible daily grind of an awful job versus the stress of being chased by a hungry bear & getting away). http://www.thepositivepsychologypeople.com/habits-of-a-happy-brain/
Most stress people feel in the modern developed world is more of a long term nagging sort, versus the survival level sort. That is also long & drawn out in such a cases, versus excitement, which in intense feeling, is generally rather brief. You don't typically sustain the anxious level excitement that impacts eating, sleeping, etc longer term. You can experience all those for a fair amount of time though when in love. It would still then be coupled with positive chemicals versus the levels of cortisol & such experienced when instead it's negative feelings you are experiencing with similar side effects.