to wave or not to wave?

so the past week, the first week of classes, i was walking to class and came up with the following predicament...
when you pass somebody, just how much enthusiasm should you put into your polite greeting? yes, we have all been told that we should say "hello" and smile as we pass somebody because it always has a positive effect on their day, but just how long do you look at them as you pass and how loud do you say it?
I feel that now it is colder it is harder to say hello to someone as you pass. i know, in my own case, i am snuggled into my scarf or jacket and don't really want to lift out my mouth to say hello and i don't want to remove my hand from its cozy pocket to wave. when i smile, the person that i am trying to acknowledge cant see my smile because of the many layers of clothing... do they think that i am rude?
Just today these awkward thoughts ran through my head, again. I went to Central Market to get some soup to keep me warm in this dreary weather. Walking past older people, whom i am more outwardly respectful to in regards to their presence, i feel that I should say hello more loudly to them. when i did that this afternoon, one lady turned and looked at me. Ageism? ya, i think so...
So, i encourage all of you to think about this as you are walking to and from classes... it will dawn on you that your walk to class isn't so mundane and repetitive. Please remember that you never know what kind of day the person is having that you are passing... a smile and a simple "hello" could change their total outlook on life...