One thing that worked for me was hanging out with people that grew up well off. I adopted some of their mentality. What was especially eye opening was dating someone who grew up wealthy and beautiful.
The most tangible example is, we would go to a nice restaurant, the host would seat us (I was happy), she would ask for a table near the window or one away from the kitchen door (no hesitation). She would always order a fun or adventurous appetizer to try new things and not finish it if she didn't like it (we always ate everything on our plates no matter what). Also if things were taking too long. she never chalked it up to we're being slighted, she was just relaxed and filled the time with conversation
To use an analogy, if we were both in a river, I was anxiously fighting against, she was gliding with flow