The key to happiness is the happiness of others. The nature functions through the law of give and take. Your willingness to give brings you closure to the nature. The more you give; the more you have of it. By being open to give you water the seeds of spirituality in you to grow. In fact, giving is the foundation of spirituality, and you should celebrate it without any expectations.
Giving without any kind of expectations increases the power of giving and that in turn enhance the level of the happiness manifold. Often expectations are the root cause of disappointment in live. If you give expecting of thanks or appreciations in return, you lesser the power of giving and cut off the natural flow of happiness, which giving might have brought into your live.
When you think of only taking and accumulation, your vision gets narrower, and you keep circulation of dynamic natural abundance away from your live. By keeping your focus only on taking you go against the natural law of give and take and attract repercussion. For instance, you cannot smell the fragrance from the flower all the time in your house premises if the surrounding of your house is full of garbage. That is why for your own benefit, you have to take care of your surrounding as well.
To conclude, life is in spreading happiness. By giving, you align yourself with the natural dynamic law of give and take. It also brings the manifold benefits in your live. Always keep in mind, giving is rewarding in their own way, the more love your give; the more love you have inside. If you give your wealth to others, they will also come to share your sorrow as well. However, do not degrade the value of giving by attaching your expectations with it. You should simply keep your attention on celebrating the spirituality of giving.