>>33914119 (OP)
You can kind of build a sense for it. Ask yourself does this woman merely see me as a means to an end or does she love me for me. At the same time you have to have admirable qualities. Nobody is loved for being a loser. So it's basically the difference between being her wish or being her wish fulfillment device. You also want someone who is your friend on top of being your lover. If you look at friends they're closer to the envisioned ideal cause it's an unselfish thing.
The best advice I can give is that love is like life. You have to be a learner, adaptable, preserving, and expect that it won't always work out yet you must keep growing. People cannot promise that feelings won't change. You won't always be able to tell before it is too late. You have to embrace it's dangers and hardships as it's part of it's beauty.