I have a some questions about Flush draws :

In poker forums many times i see players saying you have to bet here to protect your made hand against draws, yeah, I know i have to bet strong , but what does really mean not giving odds? Why I would like him to pay with the risk of being outdrawn? Why to build a pot that i wont be able to fight with confidence when a third suited card come ?

I know that it compensates for the FE, the times he doesnt hit or flopping a better hand , but I want to know the math of doing that, for doing it better and keep doing it :)

Another question is about the opposite.... how to play the flush draws optimally?

With any kind of made hand Im underdog? Even a pair is beating my in a certain point of the hand, but how i can evaluate my equity against a Tp+made hand to know how much I can pay, when to fold or when to go AI??,

For example in the turn when there is one card remainin to risk my entire stack sometimes hoping for a runner runner with A high draw, or when there is a paired board??

And the last one related with mathematical expectation and mental game problems, 

I know that in the long run if I make the most EV+ decisions I will win, but Im a human, it fells bad o lose ,oney, in my case i fell like a delay in my progress and think Im a worst plater because I ve been stuck for a long time. So I dont know waht to do to continue when i find obstacles, i dont want to play more to lose more, i ve tried to only play my best without being results oriented but I cant, what would you recommend me??

I hope some comments,, sorry for my bad English,

JJK