に気がつく => to notice; to realize N4
とかく…がちだ => apt to do, tend to do N2
Trend
~かいもなく/~がいもなく      => despite; even though ~. I tried hard / hard but unfortunately ~ N1
がなくもない => it's not that; I may (double negative) N2
Position, perspective
..は, ...が => Compare は and が N5
Compare
甲斐がない/甲斐(も)なく => it's not worth one's efforts to do something N2
てくれてありがとう => Thank you for doing A N4
Honorifics
が  => but N5
Contrast
が => But... N4
Contrast
が => Auxiliary words N5
Auxiliary words
が => Well, then N4
How to say the beginning
だが => But N2