Mingyur Rinpoche encapsulates in a beautiful quote what I've been pondering for some time, namely that the reason for acting is often more important than the action itself:
Let's say you feel moved to plant one thousand trees. If your heart is completely pure, and love for the ecosystem is your sole motivation, it's a wonderful plan.
However, it's not good if — despite your good intentions — there's a little voice in the back of your mind whispering, "This is gonna make me look really good," or, "I can't find a decent job, so maybe I should use this venture to launch an organization and make a profit." If you don't address your inner environment, even your altruistic actions can become self-interested. They can take a back seat to your personal issues. They can cause problems within your mind, or among your friends and community. The situation can get very convoluted.
Conversely, if you transform your mind in the service of helping the external world, your actions will have tremendous power. Without your mind, you can't do anything. It's the control tower, the force guiding and controlling your actions, navigating you from points A to B. If you harbor any doubts on that point, recall that in this very moment, if your mind didn't think, "Okay, time to go on to the next thing," you'd be staring at this sentence for the rest of your life. In order to be of assistance to other sentient beings, your head and heart need to be in the right place. It all starts from the inner environment.– Mingyur Rinpoche
I'm not sure there's ever a right reason to act, though – if we wait to be certain, we never do anything. But there are undoubtedly wrong reasons: anxiety, fear, anger, the need to prove oneself. It's these that one should wash away before taking a step.
Not that I succeed, mind you. But I'm pondering it.