Okay, so I solo travel a few times a year and sometimes up to a month at a time and I've never checked in a bag. I only use a carry-on which means there's usually a 5-12kg weight limit depending on the airline and I always make sure to meet it (although they rarely check unless you're visibly struggling so you can get away with being slightly over in a pinch, most airlines also don't have a weight limit for your personal item so you can put your small but heavy items like electronics in there), obviously your list will depend on where you go - going to a foreign speaking country and grandma's up the street is two different things, but for international travel this is what I bring.
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1. Clothes. Don't bring too many of them because they are heavy and take up a lot of space, instead check if your can wash your clothes where you stay. Small things like socks can be washed in a sink and hung up to dry over night so you can rotate them every day, odds are they'll get worn out from walking (if you're traveling to explore) anyway so just wear them to death and throw them out when you get home. It's also not that expensive to buy a cheap T-Shirt or two in a pinch so don't pack more than you know you are going to need. I often bring 1 set of nice clothes for occasions and a bunch of crap that I've been planning to throw out in case I need to. You can also wear layers to circumvent weight requirements.
2. Other things NOT to bring are universal utility items; shaving cream, toothpaste, sunscreen, extra razors. etc. It's a waste of space to bring things you can buy at any convenience store in basically every country. DO bring the things you might need immediately like one disposable razor, toothbrush or deoderant for longer travel. If you're flying I especially avoid liquids, you're usually allowed small <50ml bottles but you'll have to dig them out and put them in a baggie so you can save yourself some headache by just buying them on arrival. (Also don't bring unsealed food if you're flying)
3. On to the list of things I do pack every time; Small bag of toiletries (toothbrush, razor, nail clippers, tweezers, floss, a few toothpicks and cotton swabs), again if you're flying don't bring anything sharp like a nail-file (really would have helped if you said where and how you're traveling, lol), hair trimmer (I'm bald so I use it every few days), phone charger, plug adapter, small power bank (big ones are prohibited on planes), house key, passport/credit card holder, foldable umbrella, mini shoe-horn, climate appropriate headwear (ie a cap if it's really sunny, a beanie if it's really cold), sim card eject tool (if I need to buy a sim card). A book. A roll of toilet paper. A few band-aids (incase of blisters), a pen.
4. Paperworks, again it is for traveling to foreign countries. Always write down adress and booking information for places you're going to stay, emergency numbers, Visa. If you won't have internet access ticket and seat booking information, etc.
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That's about it, as long as you're getting the essentials I think it's more important not to over pack even if you're just traveling a short distance because why lug around a bunch of things you aren't going to need? I also recommend packing up to a week in advance to give yourself time to remember something you forgot.
Speaking of forgetting I almost forgot I also bring a small luggage scale (it is again for meeting the weight requirements while flying).