How can I not be a nice guy?

Don't misunderstand me... I don't want to be a bad guy. I want to be normal. When I feel I like a girl, I tend to become her friend and eentually fall in the friendzone. My flaw in relationship matters is that I tend to help people a lot. Either psychologically or in practical matters. I have a crush on a girl and I don't think it will work out for two reasons:
1) She likes someone else
2) I helped her with her crush thinking I would make her fall for me. Big mistake
I gave her advice on the situation with her crush... she needed help.. I gave her help. I have no problem giving help. I gave her too much help. And this made me fall in the friendzone. If I do this everytime I have a crush... anyways I dont. And no I dont want a girlfriend just to have one. But I have this problem where I give too much advice and help. I also don't know how to flirt properly and generally my first and only so far relationship was made with the help of a mutual friend.. and I got cheated too! What can I do? I want to help others.. but when it comes to crushes I need to drop off the advice I give. How can I control it? This with the problem of not knowing how to flirt properly... won't get me anywhere..
How can I not be a nice guy?
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