The word, "Keeper" in the Hebrew is the word, shamar. Like many Hebrew words, shamar has numerous legitimate meanings. Here are some of them, and how the verse would read applying each meaning to yourself.
 
1.   "To exercise great care over."  The Lord exercises great care over me.
2.   "To take care of." The Lord takes care of me.
3.   "To stand guard over." The Lord stands guard over me.
4.   "To protect." The Lord protects me.
5.   "To be a watchman over." The Lord stands watch over me. Day and night He stands watch over me. Verse 4.
6.   "To attend to." The Lord attends to me.
7.   "To be a bodyguard." The Lord is my bodyguard.
8.   "To preserve." The Lord preserves me.
 
Six times in Psalm 121 the word, "Shamar" is mentioned.  In verse seven, the Scripture says, "The Lord will keep you from all evil."
 
"Evil" in the Hebrew language is the tiny word, "Ra." It means, evil, wicked, hurt, bad, trouble, affliction, adversity, harm, and sad."
 
How much evil will God protect (shamar) you from? How much hurt? How much trouble? How much harm? How much sadness? How much badness? ALL!!!
 
How awesome to have God as our personal, never sleeping, never slumbering, never distracted, watchman and bodyguard!