For me, I might put something on and then promptly take it off for these reasons:
1. The color doesn't fit the season (for instance, I don't enjoy pastels in winter). When the seasons change, I usually find myself reaching for the item again. That might be why you aren't wearing your light-colored jeans.
2. The length of the top doesn't work with the rise of the bottoms (this is a biggie for me). The solution was to buy higher-rise bottoms to work with the shorter tops. I've got that sorted, and now I'm happy as a clam wearing my shorter tops.
3. The vibe is one that doesn't feel like "me" when I put the item on. Here, I have to discern whether it is the item itself that has the incorrect vibe or whether the problem is the particular group of pieces I have combined it with. Sometimes changing the supporting act for an item makes all the difference.
4. I don't have the appropriate underpinnings. The solution would be to buy the appropriate undergarments (e.g., a cami with a particular neck or in a particular color), but if I can't find the appropriate ones, then I have to decide whether I love the item enough to hold on to it until I can find them.
5. The item itself is seasonally confused. So...in the case you mentioned, with the wide V-neck sweater, it might feel too exposed for winter wear (not enough fabric at the neck). The solution would be to use an accessory (like a scarf) or layer with another item to cover up the exposed skin so you feel warmer.
I'm dealing with no. 4 right now. I have an ivory turtleneck that I really like, but the material is somewhat sheer. I am OK wearing a nude bra underneath, but the whole reason for wearing a turtleneck is that it is COLD, and that means I need another underlayer. I have two nude camis, and one is a silk one that is slightly loose on me, and when I tuck in the turtleneck, it poofs out at the waist a bit due to the cami. The other nude one looks great with the turtleneck, but it is really tight and doesn't feel good. So what should be a workhorse usually sits in my dresser. Maybe I could remedy the situation by having my cami taken in so that it isn't so poofy.