diff --git a/cmd.go b/cmd.go
index feb253c..9bc5ee1 100644
--- a/cmd.go
+++ b/cmd.go
@@ -136,7 +136,7 @@ By default, only root user is allowed to access the batt daemon for security rea
 				if os.Geteuid() != 0 {
 					logrus.Errorf("you must run this command as root")
 				}
-				return fmt.Errorf("failed to install daemon: %v", err)
+				return fmt.Errorf("failed to install daemon: %v. Are you root?", err)
 			}
 
 			err = saveConfig()
diff --git a/install.go b/install.go
index 2daa897..4564b5b 100644
--- a/install.go
+++ b/install.go
@@ -14,6 +14,7 @@ import (
 var (
 	//go:embed hack/cc.chlc.batt.plist
 	plistTemplate string
+	plistPath     = "/Library/LaunchDaemons/cc.chlc.batt.plist"
 )
 
 func installDaemon() error {
@@ -45,21 +46,21 @@ func installDaemon() error {
 	}
 
 	// warn if the file already exists
-	_, err = os.Stat("/Library/LaunchDaemons/cc.chlc.batt.plist")
+	_, err = os.Stat(plistPath)
 	if err == nil {
-		logrus.Errorf("/Library/LaunchDaemons/cc.chlc.batt.plist already exists")
-		return fmt.Errorf("/Library/LaunchDaemons/cc.chlc.batt.plist already exists. Did you forget to uninstall batt? Please uninstall it first, by running 'sudo batt uninstall'")
+		logrus.Errorf("%s already exists", plistPath)
+		return fmt.Errorf("%s already exists. This is often caused by an incorrect installation. Did you forget to uninstall batt before installing it again? Please uninstall it first, by running 'sudo batt uninstall'. If you already removed batt, you can solve this problem by 'sudo rm %s'", plistPath, plistPath)
 	}
 
-	err = os.WriteFile("/Library/LaunchDaemons/cc.chlc.batt.plist", []byte(tmpl), 0644)
+	err = os.WriteFile(plistPath, []byte(tmpl), 0644)
 	if err != nil {
-		return fmt.Errorf("failed to write /Library/LaunchDaemons/cc.chlc.batt.plist: %w", err)
+		return fmt.Errorf("failed to write %s: %w", plistPath, err)
 	}
 
 	// chown root:wheel
-	err = os.Chown("/Library/LaunchDaemons/cc.chlc.batt.plist", 0, 0)
+	err = os.Chown(plistPath, 0, 0)
 	if err != nil {
-		return fmt.Errorf("failed to chown /Library/LaunchDaemons/cc.chlc.batt.plist: %w", err)
+		return fmt.Errorf("failed to chown %s: %w", plistPath, err)
 	}
 
 	logrus.Infof("starting batt")
@@ -68,10 +69,10 @@ func installDaemon() error {
 	err = exec.Command(
 		"/bin/launchctl",
 		"load",
-		"/Library/LaunchDaemons/cc.chlc.batt.plist",
+		plistPath,
 	).Run()
 	if err != nil {
-		return fmt.Errorf("failed to load /Library/LaunchDaemons/cc.chlc.batt.plist: %w", err)
+		return fmt.Errorf("failed to load %s: %w", plistPath, err)
 	}
 
 	return nil
@@ -84,17 +85,26 @@ func uninstallDaemon() error {
 	err := exec.Command(
 		"/bin/launchctl",
 		"unload",
-		"/Library/LaunchDaemons/cc.chlc.batt.plist",
+		plistPath,
 	).Run()
 	if err != nil {
-		return fmt.Errorf("failed to unload /Library/LaunchDaemons/cc.chlc.batt.plist: %w. Are you root?", err)
+		return fmt.Errorf("failed to unload %s: %w. Are you root?", plistPath, err)
 	}
 
 	logrus.Infof("removing launch daemon")
 
-	err = os.Remove("/Library/LaunchDaemons/cc.chlc.batt.plist")
+	// if the file doesn't exist, we don't need to remove it
+	_, err = os.Stat(plistPath)
 	if err != nil {
-		return fmt.Errorf("failed to remove /Library/LaunchDaemons/cc.chlc.batt.plist: %w. Do you have enough permissions? Is batt already uninstalled?", err)
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return fmt.Errorf("failed to stat %s: %w", plistPath, err)
+	}
+
+	err = os.Remove(plistPath)
+	if err != nil {
+		return fmt.Errorf("failed to remove %s: %w. Are you root?", plistPath, err)
 	}
 
 	return nil
diff --git a/sleepcallback.go b/sleepcallback.go
index 7609fb5..a3bbcc8 100644
--- a/sleepcallback.go
+++ b/sleepcallback.go
@@ -46,8 +46,8 @@ func canSystemSleepCallback() {
 	// because there may still be a maintain loop waiting (see the wg.Wait() in loop.go).
 	// So decisions may not be made yet. We need to wait.
 	// Actually, we wait the larger of preSleepLoopDelaySeconds and postSleepLoopDelaySeconds. This is not implemented yet.
-	if time.Now().Sub(lastWakeTime) < time.Duration(preSleepLoopDelaySeconds)*time.Second {
-		logrus.Debugln("system has just waked up, deny idle sleep")
+	if timeAfterWokenUp := time.Since(lastWakeTime); timeAfterWokenUp < time.Duration(preSleepLoopDelaySeconds)*time.Second {
+		logrus.Debugf("system has just waked up (%fs ago), deny idle sleep", timeAfterWokenUp.Seconds())
 		C.CancelPowerChange()
 		return
 	}