A Prayer for Everyone
A tefillah that leaves out the whole of Klal Yisroel is hardly a tefillah, which is why our prayers are written in the plural.
Rav Pinchos taught that a prayer not said on behalf of all of Klal Yisroel is not truly a prayer. He pointed out that most of our fixed tefillos speak in the plural, asking for us and not for me. We daven with a congregation to remember that we are never alone in our needs. A person who davens by himself can still hold the whole people in his heart, so that even a private request is lifted into the needs of all Israel. Rav Pinchos was so firm about this that, according to Medrash Pinchos, he strongly warned his sons against any tefillah that leaves the rest of Israel out of it.
Source: Medrash Pinchos (Bilgoraj 1930 ed.; the passage beginning מאוד הזהיר, no numbered section in print)
Next time you daven, notice the plural words in the tefillah and say them slowly. Before you ask for your own need, think of one other person, a friend who is ill, a family looking for a match or a neighbor out of work, and include them in your words. If you pray alone, picture a minyan standing around you. It takes only a moment, and it reminds you that you carry other people and that they carry you.