The idea of "almost" or "not quite" generally means the same thing in a dream, including:
A feeling of falling short, as in feeling not quite good enough, or qualified enough, or valued enough
A near miss, such a dreaming that you almost drove off the road, which would represent a course correction in your life
Feeling you're ready for something, as in dreaming that you're almost 18 could mean you're feeling you're ready to act like an adult
Also, consider the meaning of whatever or whoever is "almost."