start up error

What I expected to happen was...:
that Minecraft would open

What actually happened was...:
Minecraft ran out of memory before it opened, so I changed the JVM argument to -Xmx2G. Then, when I launched Minecraft, Java said there was a fatal error and it closed. I played around with the JVM argument until the Java error didn't occur, but Minecraft stopped responding before it opened all the way.

Steps to Reproduce:
1. Open Minecraft launcher
2. Launch Minecraft
3. ...