I find this is a very difficult time of year for crochet. The weather is getting nicer, and sometimes altogether too hot and sticky. These are not the conditions in which you really want to be working with wool, or any large heavy crochet project. Add to that all the other things you could be doing outside and even with the longer days, there just isn't enough time. No wonder that small, portable crochet projects have become synonymous with summer.
Yet spring/summer is exactly the time a crochet designer needs to be thinking of warm, winter things. Magazines have to have time to collect content before publication. This equates to their editorial calendar submission deadlines being several months in advance. Therefore, if you design, plan on making that wool coat in the heat of summer.
As a child, I would often wake up at 6am in the summer to find my grandmother in the kitchen just finishing all of the baking. She chose the early morning hours to do this because it was "when it was coolest." Now I find myself crocheting the warmest things in the early hours of the morning. Planning, sketching, and all the other things that have to be done on paper or the computer are done during the warmest hours of the day.
As far as thought management, here's a trick I learned in the corporate world: Have ONLY ONE calendar. Penciling everything in a day planner or calendar helps avoid scheduling conflicts. What about the crochet calendar I talked about a few posts ago? I use that for the details. Whereas my personal calendar will have an entry like "start birthday gift", the crochet calendar will have the pattern, materials, etc. needed to complete it.
Just as it is difficult to go to a 9 to 5 job when it is so nice outside, it is every bit as difficult to keep yourself motivated to complete crochet projects. Think about how you will feel when your project has been completed, add a little self-discipline, and you will manage to get it done.