There are a few universal issues that plague hikers and backpackers. I will deal with three here.
You will be hiking along and a snippet of song will lodge firmly in your brain. A snippet because you won't know all the words and then it becomes a loop of a partial song and your sanity begins to wane. In really bad infestations, it's in your head when you wake up to pee at 2 a.m. and it's still there when you greet the new dawn with bleary eyes because you never did get back to sleep.
The best thing I have found to do is just treat the passing song like a snatch of music heard from a passing car. Let it flow across your brain and continue on. If it digs in, listen to it go by again and start looking for certain colors or count trees or think through your menu plan, check your map. Engage your mind and the earworm will have less room to latch on.
You can also counteract it by changing channels and singing a whole song you DO know. Even that one about Mary and her Lamb and the public school's vicious controlling ways.
<) )╯ 'Cause I just wanna look good for you
<( (> good for you
<) (> uh <) (> huh
/ \ / \
2. Wicking material starts to stink, even after washing.
As best I can tell, this is the antimicrobial features of the wicking shirt, bra, leggings and so on being bombarded by detergent and clogged up, so the material can't shed stink and even picks it up from other clothing. Washing like normal with a cup of vinegar added at the start seems to do the trick.
3. Chapped thighs/chub rub
I covered this in a trip report blog, but not everyone is into reading those, so I will do it here, too!
I discovered recently when I was hiking with bare, wet legs, that even if they are not hot at the time, chub rub can happen! Water, aloe, neosporin all HURT. What does not hurt is hydrocortisone cream. Plus, it cools the burn and heals within a day or two. I wish I had known this before!