I have a younger friend that I want to use these kind of expressions with, but don't know how to say it in Japanese. I want them to do their best and not have people take advantage of them. I feel they might be the kind of person, that would take negative things from other people to their detriment. So, I want to say something like, you have to stand up for yourself sometimes. If you don't people will take advantage of you. Any ideas?
You have to stand up for yourself sometimes. If you don't, people will take advantage of you.
You should stand up for yourself and not have people take advantage of you.
The direct and harsh translation of "Don't take advantage of someone! Stand up for yourseld" is "人に頼るな! 自分でやれ！" I'm not sure the situation, but I believe you don't want to fail at the relationship. So "人に頼らないで、自分でやってみよう！" shoule be more appropriate.
Don't let anyone take advantage of you, stand up yourself, u can do it: 他の人に優しさを利用させないで。自分で立ち上がれ、あなたの力を信じる。