I've found a trick that works most of the time. Maybe it'll be useful to share.
I get very involved with music and I have an enormous library of songs. I've put together a playlist with a sequence of songs to gradually adjust my mood, and since I can shift slowly enough, as long as I'm enjoying what I'm listening to my emotions will generally go along with it. This doesn't always work, but probably 90% of the time.
So here's what the list looks like, with just a few sample songs (my actual playlists are usually much longer, even many hours long):
First set of songs feature pure misery and despair, so I have no trouble identifying.
["King of Pain" by The Police, "Bother" by Stone Sour]
Shift to angry songs. Not a big step in mood.
["Ugly" The Exies, "Thoughtless" by Korn]
Follow that with with defiant songs. Again, it's not a big change.
["Defy You" by The Offspring, "I Will Not Bow" by Breaking Benjamin, "Do you Call My Name" by Ra]
Once I've shifted entirely from angry to defiant (it's a spectrum) shift from defiant to aggressive/arrogant/confident songs.
["This is War" by 30 Seconds To Mars, "Noise" by Tokio Hotel, "Maybe" by Sick Puppies]
And clearly, once I'm all the way to arrogant and confident, it's not too hard to start slipping a little hope in there.
["Kill Your Heroes" by AWOLNATION, "Iridescent" by Linkin Park, "Long Forgotten Sons" by Rise Against]
Finally ease into some outright hopeful and happy songs.
["Hope" by Anything Box, "Unputdownable" by De/Vision, "Elevator" by House of Heroes]
I don't know if this concept is useful to anyone else, but I figured it couldn't hurt to share. If you're interested in a sequence like this and you don't know what songs to use, let me know what sort of music you prefer and I can probably come up with some examples.