In this week's Parsha, we are told that Avraham rose up early in the morning, took bread and a bottle of water, gave them to Hagar along with her son, and sent her away (בראשית כ"א:י"ד). The Torah here tells us that Avraham woke up early in the morning to fulfill Hashem's wish even though it was against his will. Avraham undoubtedly wanted Hagar and Yishmael to stay with him. But Hashem agreed with Sarah that Yishmael would be a negative influence on Yitzchok and they therefore had to be sent away. Avraham quickly took action to fulfill the wishes of Hashem.
Aside from the natural emotional difficulty any father would have with sending away his child, banishing Yishmael was, for Avraham, the kind of behavior that was totally inconsistent with his usual attribute of loving kindness, which he displayed to everybody. He had to act in a way which was the exact opposite of his nature. But even though Avraham had to act against his usual kindness, he woke up early anyway to carry out Hashem's command. He could have easily pushed off this most painful of actions, but Avraham's main goal in life, apparently, was to carry out Hashem's will, even when that meant going against his own nature. We can therefore conclude that Avraham's focus was not on whether he personally liked or enjoyed what he did, but on doing what was right in Hashem's eyes. This self-discipline of Avraham Avinu also allowed him to do all he could for his guests, and even wait on them even when he was ill, as described in the beginning of our Parsha.
We should all learn from Avraham that whether or not we feel like doing something should not be the major question in determining what course of action to take. Rather, we should ask ourselves what the proper thing is to do right now in the eyes of Hashem. Once something is proper to do, we must then act with an enthusiasm that comes from an inner acceptance of the importance of doing what we know is right in the eyes of Hashem.