"Where this love for each other is perfect and the two share it completely, each striving to outdo the other in devotion, the marriage is ideal and worthy of envy, for such a union is beautiful." Musonius
That a relationship should be rewarding to you seems like a given, yet it is more accurately an afterthought. After all, that is only half of the matter. The other half is asking how is that same relationship rewarding for the other person? If one day passes such that the answer to that question remains unclear is one day too many. People think a good relationship is a peaceful partnership when in actuality a rewarding union is active and competitive -- a competition to see who can outdo each other in making the other person's life even more rewarding. The key here is that both individuals play along and continue well beyond the infatuation stage, demanding that your behavior must be appropriate and never extreme.
It never fails that one ignores the last sentence above and thus would have the following concern: how do you know you are not being taken advantaged of? You do not know, if you are doing it right. What you do is your main concern, without any expectation of a return favor. The relationship, if there is going to be a relationship in the first place, is one that is built on trust, first and foremost. The reason why this is important is without trust, there would be hesitation. And if there is hesitation, then there would be doubt and a lack of devotion, a lack of fun and enthusiasm. When those components are missing, you are defeated and your competition wins out.
Besides, does it really matter that later you discover the other person wasn't really devoted? You acted in good faith throughout and that is all that should matter to you. You are without blame for something outside of your control. You would, however, be faulted if you did anything less. If you gave it your all, everything you got, the best outcome was what it was, even if it was unsuccessful. Therefore, why worry or even predict a bad outcome from the outset and for certain fulfill your own prediction? With complete trust and devotion, you have a fighting chance to fulfill and maintain a union, which is as sure a guarantee in life as it gets.
In a relationship, when a problem arises, focus on attacking the problem, not the one who is beside you helping you. When something goes right, focus on sharing the success, and recognizing the one who helped you, even if only indirectly. When everything is stable and normal, extend yourself by improving and making something better in your relationship, to further affirm and strengthen the union. All these scenarios require work, but it is the type of work you find rewarding in and of itself.
Therefore, Epictetus, when a girl decides to hold your hand, you can decide to reciprocate, too. Realize, however, that she can also choose to later let go if she doesn't want to walk beside you anymore. Thus, be sure you do all you can to make the walk worthwhile for her. If she is a good fit for you, then she would do the same. If it doesn't work out, do not assume there was anything wrong, for trying to find a match and realizing something doesn't fit are rather common and natural. What is super is realizing a beautiful existing union, one worthy of not taking each other for granted, of trying to earn each other's keep each and every day.
"Do not tell people what they should do when you do what you should not." Musonius