Roaring Bull Market

Do bulls roar? Do markets roar?

I don't know what to do in this market. I don't understand it.
It scares me.
Too high!
Why is it shooting up today?
Is it a short covering rally? All the people who sold short expecting a May correction are now wildly covering and driving the market up and away?

Or is it reasonable.
Markets have a long way to go now.
We have really had a stagnant market for 10 or 15 years and now markets can double
DOUBLE
and it would not be unreasonable.

What am I doing?
I am scared.
I am sitting with cash. Option premiums are very low.
The odds in my mind favor a continued move up. But there is the fear of a correction or a crash.

Here is how I am thinking

10% continued rapid rise
10% crash
10% correction
20% slow rise
50% nothing to write home about.

Corrections are usually short and bitter.

So sitting in cash I fear I will miss the 30% chance of good gains over the next two years.

I  really don't have any good ideas right now.