We humans, were designed to be social. To go against that notion goes against our very nature. At the very center of our view is our individual self - our individual mind - our soul. Therefore, knowing we we our individual selves need, we can reason that other rational beings need the same things. We ought to have compassion and we ought to share and have compassion towards others.
One of the concepts that helps me have love towards others is the concentric circles. Some call it the circles of compassion. The Human is Contemplative blog does a great job describing this concept:
Hierocles used concentric circles to explain the oikeiôsis, which could translate as appropriation. The first circle is our own minds, the next circle outward is our immediate family, then extended family, community, country, and the entire human race. The stoic endeavor is to draw these outlying people closer and closer toward the inner circles with respect to our concern. Thus, the process of oikeiôsis in human beings is one of expanding our identity of 'self' to encompass everyone. This has also been described as the stoic notion of brotherly love.
The next time you are commuting and someone cuts you off, give them the benefit of the doubt - bring them into your circle. Viewed differently, you should pretend it was you who just cut someone off. What "excuse" would you offer as an apology to the person you cut off?
In summary: put yourself in other peoples' shoes.
(see also Citadel, p.42-43, 312)