All you have to do is keep writing!
What I did recently was start a different writing project. I thought I could do a Young Adult novel quickly, if I do 2,000 words a day. This is what happened. I started well. I managed approx 2,000- 2,500 a day ....That lasted only a few days, before I ran out of steam. I have about 11,000 words of that done.
But I have already had 2 other projects on the go:
1. Deep in the Cocoa, to be edited ....again
2. A new version of God in the Cocoa, a prequel to the above.
So that I don't have to decide each day what to work on, I decided to work on one project for a full week. So every project would come round again every 3 weeks. OK!
That was working out fine.
I got bored again :(
I thought I might start something entirely new ...a Romantic Novel :))
That lasted for 2 weeks, and I have 15,000 words on that.
Now I have a total of 4 projects on the go properly. That is apart from all the ideas that I write down every day.
This week however, I have returned to one of my original projects, God of the Cocoa. I have planned, and replotted this version. It is totally new, and I am very excited. I am now working more-or-less to a planned plot. More or less!
I do find though that it is so easy for me to go off course...But it isn't my fault. It is the characters that take me wandering, I get friendly, and go along with them. Are they right, I wonder? Let's find out. And before long, I've added a few friends, because Latchmin, aged 11, was lonely.
But I have to ask myself the question, before I've wasted too much time writing their story. Shall I keep this, or delete it? Inevitably, I keep it, somewhere, because I might need it....sometime.