My brother did invite me to the concert of the Wise Guys, a German acapella group. They are one of those special groups who are able to give a cheering live show and have this special cheek-in-tongue humour in a fair amount of their songs. This is the selection that helps me keeping my mood up though, you are invited to dig further.
Jetzt ist Sommer: This was the first song I heard from them and got me interested to dig further into this band. And yes, it's true, summer is an inner feeling, not something governed by the outer world.
Lass die Sonne scheinen: I have the feeling that this is a sequel to the former song. And it definitely helps too.
Am Ende des Tages: No matter how your day went, what matters most are the people you think of at the end of the day.
Hope you are able to appreciate them as much as I am. At least they are able to cheer me up a fair bit.