Is it true that the more past relationships/breakups someone's been through, the more jaded they become?

My most recent breakup was with a woman I dated for 3 years. It was brutal because I thought I would marry her, and she even said she wanted to spend the rest of her life with me, but then dumped me a mere 2 weeks after saying that. It messed me up for a long time and even 2 years later I still have trouble trusting women, because I know they could say they love me and want to marry me but still blindside me the next day and leave me like I never mattered to them.

I've only been through 2 breakups in total, and I can't even imagine how much more jaded I'd be if I had been through 5+ breakups.

Is it true that the more relationships you go through, the less excited, optimistic and vulnerable you'll be towards the next partner? And if so, does that mean it's better to date people who've been in fewer relationships so they're less jaded and have less baggage?