I think that today is the day to do ~, but I always end up not being able to do it and feel ashamed about it.
こんにちは。
ご質問ありがとうございます。
"I think that today is the day to do ~, "=「今日こそ~をする日だと思います」
"but I always end up not being able to do it"=「でも、いつもそれを出来ないでいます」
"and feel ashamed about it."=「そして情けないと感じます。」
ご参考になると幸いです。