Fix MacBook Can't Boot Up

 You can fix it by yourself. Follow instruction below :
Upon restarting your Mac, press the Shift key.
Hold the Shift key until you see a White Screen with Gray Apple icon and eventually a spinning gear.
When you see the Spinning gear, release the Shift key.
Allow the Mac to continue booting up. Also this may take a little while
This may take anywhere from 5 to 15 minutes to load to the Safe mode screen depending on the performance of your Mac, but if it exceeds this time, shutdown your Mac and try just once more. It may have just frozen up the first time around for you.
You are going to enter the Safe Mode (which looks like your main desktop environment the only difference is certain startup items are disabled.)

Once within the Desktop in Safe Mode
From the Finder Menu, click Go> Go to Folder
Type in this line: /System/Library/StartupItems
This is going to take you to the System Library folder which has all of your Mac OS X Startupitems.
Remove all of those folders to the Trash.
Reboot your Mac normally and see if you can access your normal User desktop environment.