There is a source of perfect love and grace within us all, and until we find that foundation for ourselves, loving others will always drain us. This could be perceived as a negative assessment of love, and could discourage you from sharing love with others- but this is entirely not the case. In fact, it is the exact opposite.
We go about our lives; we have good days and bad. On the good days we may smile to the man who bags our groceries, and on the bad we may not make eye contact with a friend or drive too fast to work. We believe that these moments, which make an impression on us, are either harmonious or stressful. The decision is rooted in our perception, and it affects how we digest these experiences.
But the real truth lies beneath our conception of the feelings we create for ourselves. The origin of everything- every laugh, every smile, every tragedy, every loss- is a fountain of infinite enchantment, always present and always waiting for us. The secret lies in the moment we decide for ourselves that every single thing we do or say or feel about others has its source in love and grace. Until that moment, we cannot actually give the true source of love and grace- only a component of that love. An energetic cousin. This is the factor that drains us, because it has not come from that infinite source.
This does not mean that you should not give your love to others. It means that the only thing you truly can give is love. That any other way is draining. I understand that to surrender to this concept, at first, may not seem natural. We have been conditioned to believe that life is hard, that bad things can happen to good people, that happiness is rooted in particular monetary or sexual situations. But maybe try it for a day. Take the leap. Tell yourself that you love yourself, that the reason anything has happened to you is love and watch the events of your life begin to change. The entirety of the world will unfold before your eyes and it is beautiful.