What exactly happened???

Things were going along pretty well for a while there... I felt like I was really starting to get a handle on eating and working out and then I got sick. I was sick for a few days but then started to get back to my normal routine. I can't honestly say that I ever recovered completely from being sick because I never reached a point where I felt fantastic - which is how I usually feel after I'm sick. But for 2 weeks I chugged along and felt okay. Last week I started to feel exhausted. Friday was horrible, I blew up at two classes... Saturday the school had a fair and I had to work all day, 8 until 6:45 - that was pretty miserable. I came home Saturday night, felt like real crap and was in bed by 8:30. Yesterday I spent most of the day in bed. I had some breakfast and took a nap. Ate lunch and took a nap. By the afternoon I was starting to feel human again. I slept pretty good last night and this morning I feel okay. Not 100% but maybe about 75%. I have the day off because we had the fair on Saturday so I'm hoping by tonight I'll be back up to 100%. But how did I go from not getting sick much at all to getting sick twice in one month?? How did that work??? A funny thing yesterday, I haven't been smelling much at all for the past couple of days and yesterday I started smelling my neighbors cigarette smoke I knew things were improving. I really have to tell him about the e cigarette. He has kids and really shouldn't be smoking for a huge variety of reasons. Okay, I have some stuff that I have to get done today so I'm off..... Hopefully I'll feel much better by tonight....