I'm writing to a group of people hence plural 'your' and reflecting on their progress over the past year -
"I will think back on your journeys' with a smile"
Or no apostrophe ...
"I will think back on your journeys with a smile" (or words to this effect)
Im pretty sure it needs the apostrophe as the journeys are the possession of the 'your' (plural group) but I am doubting myself!