Set your target date with some wiggle room—it shouldn’t be so far out that there’s no pressure at all, but it should be achievable.
How much time can you devote to writing right now? If you have a ton of outside work to do, you may not have the luxury of being able to devote an hour or two hours to writing every day. You may want to have your novel written by the end of the month, but that might not be realistic. Set your target date with some wiggle room—it shouldn’t be so far out that there’s no pressure at all, but it should be achievable.