Yes, Guest, "unsighaft" makes more sense: non-victorious.

My shameless (- totally uninformed, probably unsinnighaft -) guess about the gist is: "Now that spring has come, we should be shameless. My lady does not want me, so I may as well get me a second one".

For more accuracy, we had best rely on one of the many existing books about Manesse (cf. also Neidhart).