I made plans to do ... for three months, but it only lasted two days.
I intended to ... for a few months, but I gave up after two days because I wasn't motivated enough.
ーI made plans to do ... for three months, but it only lasted two days.
「３ヶ月…をする計画を作ったが、たった２日しか続かなかった」
to make plans で「計画を立てる」
to last で「続く・持続する」
ーI intended to ... for a few months, but I gave up after two days because I wasn't motivated enough.
「数ヶ月…をするつもりでいたが、十分なやる気がでなくて２日で諦めた」
intend to で「〜するつもり」
to motivate で「やる気を起こさせる」
ご参考まで！
カナダ 
