A question of the sort that drives me crazy arrived in my In Box this week:
"I love to write and I have all these great ideas stuck in my head, but every time I start to write something I can never finish it. I don't know why but I lose interest practically the day after I start it. Any suggestions on how I can start something and actually finish it?"
You haven't told me how old you are, but my reaction is that you don't really "love to write" as much as you love the IDEA of writing. Writing is very hard work--drudgery, in fact. It's also likely that the "great ideas" are really much too big and complicated. My suggestion: pick the simplest of those ideas, one that you can finish in a single sitting, and don't get up until you've completed a first draft. Put it away, and the next time, try another idea. Go back to the first one and rewrite it. Then rewrite it a third time. Build discipline, and stop looking for quick fixes. There aren't any.
That's probably not what the frustrated would-be writer wants to hear, but it's the truth. I could add a lot to that: keep a journal; write a paragraph every day of something you've observed; listen in on a conversation and develop it into dialogue.
The secret, of course, is just to keep writing. No matter what.