I need to find out how to finish anything I start. Help me. Please.

I am a horrible finisher. I would consider myself reasonably smart (my IQ scores have generally kept between 125 to 148), I am considered a creative asset at the workplace, but the one thing holding me back is my ability to finish a project. And this is true of almost everything I undertake; I have a track record of unfinished projects that shame me into seeking help. My projects folder is full of projects I started but left incomplete and unfinished; at work I have not yet finished this project that should have been completed by now. This character flaw is undermining all my strengths and I have to combat it at any cost. Any advice would be appreciated.