Focus on the tasks that are immediate and get it done right away. Do not procrastinate! Never say that you can do it later. Prioritize. There is no better way than doing it right now.
If you wait for the right moment to get motivated for starting a work (especially if the work is undesirable), the more you delay starting, the more difficult you may find to get into the right frame of mind. On the other hand, getting started is a better option as the feeling of completion will trigger more positive thinking than leaving it undone. You can improvise on the work as you progress.
When you start your day by doing your most important task, it will give you a sense of accomplishment, and you will want to maintain this momentum the whole day.