It's good to see you again.
またお目にかかれてうれしいです
It's got everything to do with you.
全部君の問題[せい]だ
It's got sentimental value.
それには愛着がある
It's gotten slightly colder.
少し寒くなってきた
It's great fun walking along the shore.
海岸を歩くのはとても楽しい(◆((米略式))ではvery funともいう)
It's great in theory, but in practice it sometimes doesn't work.
それは理論的には結構だが,実際にはときどきうまくいかない
It's great to see you again.
また会えて本当にうれしい
It's guaranteed to give anyone a hangover.
それはだれでも必ず二日酔いにする
It's handy having you around!
君がいると助かるよ
It's hard to see [say, imagine] ....
…は理解し[言い,想像し]がたい