This is the 52nd most frequent Swedish word.
allt
"Allt" means "everything" or "all" in English.
In this sentence, 'allt' is used metaphorically to mean 'everything in general' or 'the situation as a whole', affecting the person's feelings.
Allt känns bättre nu när solen skiner.
Everything feels better now that the sun is shining.
Here, 'allt' functions as a determiner equivalent to 'all' in English, specifying the total amount of what was needed to be spoken.
Det var allt jag behövde säga.
That was all I needed to say.
The word 'allt' here is used as a pronoun referring to 'everything', indicating the entirety of knowledge or information about a specific topic.