set your sights high/low
set (one's) sights high
To have very high expectations or ambitions. You have to set your sights high if you want to have a fulfilling life. We had a really great year for sales; now let's set our sights even higher!
set (one's) sights low
To have low expectations or ambitions. My brother's attitude is that, if you set your sights low, you won't be disappointed by life.