Size shouldn't matter. Right?

I am the same person from one day to the next, al beit I am slowly shrinking in size but from one day to the immediate next I am the same person. Why is it that what the label on any particular article of clothing make a difference in how I feel? The scale is going down, I am getting in better shape so why is it that not being able to get into any particular size or getting into a particular size can have such a drastic effect on my psyche?

I have recently been able to get back into a pair of pants that I had outgrown. This prompted me to go shopping in my own closet only to find that two other pairs of pants I haven't worn in a very very long time had the same number on the label as those I just started wearing again...sadly they are not the same size! Despite the labels saying they are both the same the others are much smaller! See? So with this as absolute proof that every size is different even if it says its the same as another does what any particular label says bother me?

And now for the opposite spectrum....why if I am the same person struggling to get out of my fat clothes should the fact that by some twist of cosmic fate I can actually put a skirt on that has a big fat M on it can make me so giddy? It doesn't matter to me that this is not how the skirt is suppose to fit just that I can get it on and, yes, I purchased it and thought that maybe, just maybe I would look smashing in it by the time I go on my goal weight celebratory cruise next February. Here is the not so good mobile pic I took the day I first tried it on...

I know that size shouldn't matter but sometimes it makes a difference in how I feel. Anyone else feel the same?