On and at

Air agus aig

Usually we must say that feelings are  oirnn  (on us), using the preposition  air  (on).

Tha amharas air.
He is suspicious [lit. suspicion is on him].
A bheil (an) cianalas orra?
Are they homesick [lit. is the homesickness on them]?
Tha (an t-)eagal orm.
I am afraid [lit. fear is on me].

Sometimes we need to use both prepositions  aig  and  air  to talk about feelings. The words  gràingaol  and  gràdh  all use both. 

The feelings are  aig  the person, but they have them  air  someone or something:

Tha gràin aig Iain air a' phrògram sin.
Iain hates that programme [lit. There is hate at Iain on that programme].
Nach robh gaol aice air Seòras?
Didn't she love George [lit. Wasn't there love at her on George]?
Saoilidh mi gu bheil gaol aige oirre.
I think he loves her [lit. I think that there is love at him on her].
Tha gràdh agam air an duine sin!
I love that man [lit. There is love at me on that man]!