“all of a sudden these lights are blinding me” - the paps/photographer’s flash on the cameras, not really acknowledging them when being around Louis and the boys because he’s too focused on them. but now they aren’t there with him - absorbing his attention - he’s starting to notice how bright the lights are.
“I saw in the corner there is a photograph, no doubt in my mind it’s a picture ofyou”- there’s constant picture and stories about the boys in the papers and magazines. there’s constant stories about the boys and their girlfriends. Harry is able to predict what the photograph is of without even seeing it. He just knows what it is and doesn’t want to look because it’s too painful
“I’ll keep my eyes/arms wide open” - like saying ‘I’ll be open to the idea of these fake relationships to minimalize the rumours (and such) and i’ll keep my eyes open for the truth within the stories’ also 'i’ll always be here to protect and comfort you, i’ll always be your rock and home, i’ll always be yours for anything you want and/o need. I’m yours’.
“seems like these days I watch you from afar” - Harry can’t be seen with anyone with being label as 'dating or fucking them’ (females more than males); so it’s difficult for him to just be with people, instead he has to go low key and be distant from people he can be labelled with. Moreover, these day Louis and Harry aren’t aloud to show public displays of affection as apposed as to a year ago. this is like saying 'I can see you and can touch you so easily but I can’t because your so close but so far. instead i’ll just watch you, even though it’s agony.’ It can also be about Harry constantly being in different countries to the others (especially Louis). This was written in November, the following month Harry spend in America on his own, he could only see his Loved ones from afar.
“tired of feeling/sleeping alone” - Harry doesn’t deal with hate and being without his Loved ones at all very well. Louis (and the boys) have a more 'thicker skin’ against it so to speak. Harry feels as if he’s on his own with the distance between them and he’s sick and tired of it. He’s tired of not having Louis (and the boys) next/near to him when he sleeps - like back in the day.
Or in another opinion all of the above except it’s not Louis it’s someone else. Maybe there currently isn’t anyone but he wishes there was.