In a perfect world, with amount of free time and without distractions, you would not have excuses not to write on a daily basis. But this is not the case.
A method you can use, though it may not always be nice, is to set deadlines. Not a great final objective, but some intermediate ones. This helps get the complete novel out of your head, which is far in time; and it allows you to focus on a closer goal, easier to be accomplished without hardships.
This system rests in the need our brain has to compete and to try to win. We can use this tendency to achieve whatever we want.
I am not sure if this happens to you, but I often find that my brain does not cooperate all that it could. There are times when, for no apparent reason, writing becomes heavier. I have an idea, I like the development, I want to write it, but I feel that it is a long sorrowful process and the end seems so far away…
Setting an intermediate objective, even if it is completely arbitrary, can make a great difference. Mainly to let our brain regularly get its portion of satisfaction for a task accomplished.
It is a trick, I know. We will not get any reward, nor penalty; but, the simple fact of having a closer finishing line, will make our brain want to cross it.
Of course, there are negative aspects in this method. Even though you can keep motivation until the end of the project, it may also give the false impression of work accomplished, undermining the desire to keep going. If you focus too much on the sprint to achieve that intermediate goal, you will faint without any force left in you after you have crossed the line, and, the unfinished manuscript may end up in a drawer, languishing until you have strength to return to the path.
The alternative would be to fail that intermediate goal, which would lower our morale and make it harder to carry on with the rest of the work.