Learn Italian: Cammino tutto il giorno e i piedi sono stanchi.

In Italian, you usually do not use possessive words like miei (my) with body parts if it is obvious whose body it is. Because the sentence says cammino (I walk), we already know they are your feet, so you just use the definite article i (the).

What is the difference between tutto il giorno and tutti i giorni?

tutto il giorno means 'all day' or 'the whole day', which fits perfectly here because you are talking about a single continuous day of walking. If you wanted to say 'every day', you would use the plural form tutti i giorni.

Why does stanchi have an 'h' in it?

The singular word for tired is stanco, which ends in a hard 'c' sound like a 'k'. When you make it plural to describe i piedi, the spelling changes to stanchi. The 'h' is added to keep that hard 'k' sound. Without it, stanci would be pronounced with a soft 'ch' sound.

Why is there no word for 'I' before cammino?

In Italian, the ending of the verb tells you who is doing the action. The -o ending in cammino already means 'I walk', so you do not need to add the subject pronoun io (I) unless you want to add special emphasis.