I just got done riding my softail heritage hard and when I tried shifting down I couldn't!! It's stuck on 5th gear. I had to ride it all the way home of on that gear. Any idea how to fix this problem.

 

Hello and welcome.
If possible provide year of bike and some information so that we can get an idea.
We can not see the bike so it is rather difficult to guess.
A wild guess is that the lever arm at the transmission shaft...the lever arm that has a rod attached to it at transmission end.... you can easily see it with no tools.
That lever arm might be loose...to be specific the allen bolt that tightens that lever on the transmission shaft was loose...if lucky, a simple reset of lever arm position and tightening of the allen bolt with some blue thread locker might be enough.
If unlucky and someone has postponed service and ridden with sloppy shifting for a long time then the lever is stripped and requires replacement...on a five speed that is a big job, on a six speed it is much easier.
But that would be a wild guess since i do not know if the bike ever ran correctly, if this a rebuilt accident bike, if something was changed lately or any other information.

 

First, I truly appreciate your quick response! I was riding my '04 Softail Heritage that day when the gears freezed up on me. I'm going to be putting it up on a rack soon and will begin disassembling. Just wanted to know where to start.

 

Start with Google/YouTube. 04 Heritage stuck in gear.

If it looks like you're about to get in over your head, take it to the shop. If you're feeling brave, come back with what you've discovered.

 

Good chance you have a broken spring on the shifter pawl. Move the lever both ways, and if it doesn't return to center, the spring is broken.

 

If it is the shifter pawl spring...do not ride it