There's a lot of good advice here, but I'd like to offer another perspective: since you consider this a personality flaw, perhaps you should consider if the pro

There's a lot of good advice here, but I'd like to offer another perspective: since you consider this a personality flaw, perhaps you should consider if the projects you choose are well suited to you. As an example, would you make a better farmer or a better chef? A farmer deals with many short and long term projects: choosing and planting crops that will take the entire summer to grow; looking after the soil over the course of many years by rotating his crops; planning and executing a large scale harvest in the short few weeks that the produce is ripe. On the other hand, a chef thinks day to day and minute to minute. Planning a menu for next week's meal; finding the ingredients; taking orders from customers as they come in over the course of an evening. Both these occupations are valuable, but require vastly different skills and mindsets. Maybe you're trying to be a farmer when you'd actually make a fantastic chef!