I can relate to many of those feelings. A conversation with a coworker yesterday led to me realizing this:
In Support, we get small wins all the time. Potentially many per day. You might grind for a while on a particularly difficult issue, sometimes for up to weeks, but you get there. Most take far less time than weeks. Time between successes is usually measured in hours or days.
In warehouse equipment Sales (and others I'm sure too), you grind and grind for weeks/months/more hoping for the big sale. You may spend all year to get the one big sale that makes it all worthwhile. Time between successes is measured in months or more.
A mental shift is needed to expand the timeframe in "X successful activities in Y timeframe to feel like I made a difference". It's simple, but not easy (at least for me).
Thank you for letting me borrow your therapy couch. I'm getting up now and getting a snack. Can I get you anything while I'm up?