the half way point

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I am feeling a mixture of pride and frustration with my goals right now. I am proud of my fitness accomplishments (met my 5k goal and at 8k so almost to my 10k goal) and of my weight loss (hit the healthy range for body fat percentage) but I find myself worried about a few things....

i am gained about a pound and a half over the last week. I am pretty sure it is muscle gain... i have noticed that I wont loose any weight for a few weeks then suddenly will drop 3-4 lbs fast. But i am worried that this is a sign that i am hitting that home stretch that people always talk about.

Any tips for getting through that?

Also, winter seems to be hitting NY with force (yes it is only Oct, at least that is what my calendar keeps telling me). This will be my first winter trying to stay fit on the East Coast (I am a native CA girl). Any tips for managing working out and staying motivated for walking the half mile to the gym in cold weather/snow? Perhaps tips on home workouts that can help balance a loss of cardio?