It's been an accepted practice with the Rebbeim of Chabad from time to time to focus their mental, meditative attention on their followers. Just as a water surface reflects someone looking at it, this type of focusing leads to a strengthening of connection between the Rebbe and his follower.
This is the reason that at times and suddenly a person feels this pull of connection.
This phenomenon is akin to receiving messages from Above reflecting the concept of “shuvu bonim shoyvevim” (return, you wayward children), meaning that even though we don’t hear them physically, our metaphysical selves are capable of receiving them. This is a kind of spiritual "email" that has an effect on the soul in the body and this prompts the person to stirrings of repentance. Along the same lines, that’s how it is with the righteous who are likened to their Creator, who are able to affect this matter of connecting.
As is known, this arousal to connect to the Rebbe doesn’t come from the person but rather from Above and because the Rebbe thought about him or her and, the person is obligated to utilize these stirrings that’s “not his” in action, which is his/hers!
Even when a tzaddik is present in his physical body, he’s able to "broadcast" these waves of arousal. How much more so when a tzaddik isn’t limited to physicality (his body), it becomes then even easier to connect to the Rebbe. And every year this capacity increases.
משיחת י' שבט ה'תשכ"א