if you have a dream, are you sure you can do it?

Last time, when i have an assignment which entitle: " If you have a dream, you can do it?"
I am thinking that it maybe write like this " If you have a dream, you can do it." or it can be write like this also, that is " If you have a dream, you can do it?"
Maybe we can say like this, if you have a dream, then you try to work hard and fulfil your dream, and that will be your motivation to work hard on it。。 At least, you have the goal to achieve...
But if you don't have the dream, you may not have the goal to achieve and you have not destination to go and you won't work hard on it... And you may just do it simply...
When you have a dream want to fulfill, you may work hard and tell yourself that you can do it even on the way you face the obstacle and have to tackle the obstacle before you achieve your goal...
So, for me, if i have a dream, i will work hard to make it become true...
Wish every one can do it also...Himneseyo..