Soulmates are made, not found.
Which is to say — relationships are work. And finding someone you are compatible with doesn’t mean you are done with hard work. Once you are in a stable long-term relationship, you are always growing and evolving both separately as individuals and together as partners. And working towards being the best partners to one other is a huge part of that.
I think it’s easy to say or think that 1. Soulmates are real and the perfect person is out there waiting for you, and once you find them then things will finally be easy, or 2. Soulmates aren’t real, so you don’t need to worry about that expectation; just find someone you are compatible with and enjoy spending your time/life with.
But for me personally, I have found so much happiness in my life by treating my relationship with my spouse like something bigger than just the two of us, that we both put the work into to maintain and grow. We make each other better, and we feel like we are always becoming better versions of ourselves with one another; I think that’s a great litmus test for a ‘soulmate.’