1. Not everyone who "hangs with you" is your friend.
This is one of the hardest things I learned. You can be so close to people, trust them with absolutely everything you have and think they are always going to be there no matter what. Maybe you can't imagine your life without them and you have been through a lot together, that means nothing sometimes. I had the best friends, they meant the world to me and I still miss them every day in life, but they turned their backs on me after a drunken fallout in which we were all at fault (mainly one of the other girls). It hurts me to the core to this day however that's just down to my nature, I don't move on from things easily although I do appear to. One of them we had been best of friends for 13 years and the other I had been close with for 4 years, and although myself and my longest friend talk now it's a few texts a month if you're lucky, the friendship just withered away and died and it's pretty sad. The other shorter friendship although it was shorter through those years she had been my rock many times. I never once could of imagined she would turn on me the way she did and spite me the way she has, it still hurts. I am such a loyal person, and although they have hurt me more than words could even describe I will always miss their company and friendship. This has taught me not everyone who claims to always be there no matter what will actually always be there, only depend on yourself and never let yourself get to the point your happiness is dependant on another human being.
2. Your life wont work out how you planned.
This is one I've learned a lot through different stages of my life and it's scary not to feel in control of your own life, unfortunately that's the harsh reality though there are lots of things we just can't control and we need to learn to deal with that in any way we can. You can think you have it all planned out and things may even seem like they're going to plan for a while, but life has a funny way of messing up those plans and interfering when you least expect it. I thought I'd have a long term boyfriend and kids by 21, that's what I'd always wanted, instead I got a "fuck boy" who broke my heart and multiple miscarriages by 21. I'm now 24 years old and finally met someone who treats me right and now I'm ready to settle I'm now facing uterus abnormalities which may affect my chances of ever having a child. Be grateful for everything you have in life as someone may be praying for everything you already have. Life has taught me to take nothing for granted because you never know when it can be taken from you.
3. Not everyone has the same values and principles as you.
You may not agree with cheating, breaking promises or lies or any other thing you can think of, however that doesn't mean others are going to act the same as you or do what is considered "right" in your eyes, as they don't have the same values and principles, some people simply don't have any and that's something else which can be quite difficult to grasp especially when you have strong principles. Just because you don't do something doesn't mean others won't do it to you I still struggle with that sometimes. When things hurt me they hurt me bad, and I can't get over the hurt easily, it really kills me for a long time, years and years my mind will run over it thinking "how could they do that" when most others would have moved on, and that is simply because I could never do those things and the way my mind works is if I can't do it how could they? They must hate me. Deep down I know it isn't true and I try not to let it affect my life so much anymore and I try to remember everyone has different principles and some people just don't care enough regardless how good you are to them - don't let this affect your self worth 'cause it says more about them than it does about yourself.
4. Not everyone has the same heart as you.
You may be the most loyal friend/partner/relative/person in the whole entire world but that certainly doesn't mean others will have the same heart as you and treat you the same. You could bend over backwards to help someone out, in terms of giving someone your last penny, babysitting, lending them clothes, lending them a shoulder to cry on, and they may also seem very grateful and thankful to you at the time, however a lot of the time when it comes to you needing the favour returned however many days, weeks or months down the line they are nowhere to be seen, or don't offer any sort of help, no financial support, no shoulder to cry on, nothing. Don't let this dishearten you as I have let it dishearten me in the past, just be grateful you are the better person and never let the cruel world change the amazing person you are.
5. Self worth means more than any opinion of anyone in the whole world.
You could be the prettiest girl in the world with the most amazing figure but if you don't like what you see or you have negative thoughts about yourself you will never be happy, because no matter how many compliments you receive off someone if you don't one hundred percent believe it in your own head the compliments don't really mean anything. I have learned the hard way; it's all about what's going on inside your own head and at the end of the day that's all that really matters. Of course it's lovely to feel loved and beautiful by others, however if you don't feel worthy of those comments you will never believe them. Happiness starts with YOU. Never forget that. Focus on you, tell yourself each day at least ONE thing you love about yourself. Don't criticise yourself for small things, don't be too hard on yourself or critical on yourself for minor things. Love yourself, be you and the right people will love and support you in all your endeavours and lift your spirits higher than ever before.