Take a few moments at the end of each session to consciously extend the positive energies that you have accumulated. Radiate that energy outward as light and love, and imagine it touching others as a vibration that calms, energizes, heals, comforts, and nourishes. Be creative! Imagine you are playing a mental video game. Beam all your postive feelings to your friends, family, people you feel neutral toward, even your enemies. Realize that they all, just like you, want to be happy, want to escape suffering and pain and make the most of their lives. Thus, in your own way, you can make the world a more peaceful place to be in.
In this way, you can see that the time you take to master stress is not selfish. In fact, it is an active form of accepting responsibility for and contributing meaningfully to the lives of others. Though at first these mental training techniques may seem imaginary or conceptual, with practice you will find that you are helping - yourself and others.
I find it very beneficial to reflect on the universal motivation - that is, the desire to be happy. Everyone wants this and that realization helps me contemplate my connection with all beings. When I meditate, I am helping myself learn how to be happy and I then reflect, since I am connected to others, that my happiness is connected to their happiness. This helps me in my willingness to share the benefit even with people I experience as difficult.