It's often said experience is the best teacher, I heard this a lot growing up. I also learnt it's better to learn from the experiences and mistakes of others than go through them yourself. I think that's a really wise thing to do, although it can breed fear if you're not careful. You get scared of failing which will in turn make you not take chances.
I've learnt to take the leap when opportunity presents itself despite the fact I've seen others fail at attempting such opportunity. You really would never know until you try.
Another lesson I've learnt is that you can't pour from an empty cup. First, you nurture yourself and mind, before thinking of someone else.
Tolerant people tend to take a lot of nonsense and sometimes let people walk all over them, I've learnt to put a limit on how much of such nonsense I can take. You can't please everyone and if they're gonna be mad at you, then so be it.