While your bond with this person will be strengthened by a powerful and enduring past-life connection that you share, it won't make for a fun, romantic affair. There's a good chance that if you become romantically involved, it will last long-term; after all, you're coming from a relationship in another lifetime that persevered through hard times as well as good ones, and has extended to the present life. A sense of mutual responsibility will pervade your connection now, as a result of this past-life relationship, and you'll both sense this from the start.
But it's quite possible that you will be attracted to this person more because of this past-life connection than because of any sense of common interests or physical desire in the present life. You'll feel a sense of duty to them, or even obligation, as if you owe it to them to become intimately involved simply because you did so in another life and you've found each other once again. But you don't owe them anything, and the type of serious relationship that will result may not be what you need any longer. Your partner will try to keep things quite serious, however, even when you try to lighten up the atmosphere between you with flirtation or other romantic overtures. They might even reject your advances, which could hurt you if you don't recognize the true, underlying reason for the rejection: Deep down, your partner is likely afraid that you will leave them, or break their heart. That vulnerability is something everyone can relate to, so use your sense of compassion to soften your responses to your lover. Try not to commit to them romantically until you get to know each other well enough to know that this relationship is truly what you're looking for.