To Luck
"we were told never to put our faith in you", he is saying that he was told never to believe in luck which is wrong because you should always believe in everything. you should have faith in everything even if you dont have luck all the time it is still there. everything God made is real whether you believe it our not and when you stop having faith in Luck then thats when you lose luck.
The summer day
"this one who flung herself out of the grass", i think this is talking about how beautiful nature is and how each animal looks different and moves different. the grasshopper is unique because it is an animalthat chews side to side and jumps out of the grass unlike other animals who cant hop or jump. it also has a unique color that makes him blend in with the grass. she is also saying live life to the fullest.
Late for summer weather
"he a dirty sweater, she an old blue coat that fits her tight", i think its saying they are kind of poor and that all they can afford. those are not summer clothes because they dont have enough money to buy summer clothes and thats why they are late for summer. they also like to relax and hang around doing nothing.