I think undivided attention is more "focus" and is deliberate. If you don't want or like "it" then it's obsession or fixation rather than focus :-)

Friendship marks a life even more deeply than love. Love risks degenerating into obsession, friendship is never anything but sharing. ~ Elie Wiesel

I have an intense obsession with making films. I not only love to make films, I perhaps need to make films. ~ Jacqueline Bisset

Obsession is the single most wasteful human activity, because with an obsession you keep coming back and back and back to the same question and never get an answer. ~ Norman Mailer

Obsessional does not necessarily mean sexual obsession, not even obsession for this, or for that in particular; to be an obsessional means to find oneself caught in a mechanism, in a trap increasingly demanding and endless. ~ Jacques Lacan