You might work two jobs for a while. That’s not failure. Plenty of builders funded the dream with a day job.

Holding two jobs looks like a sign of things going badly and is more often a sign of something being built. The ordinary job pays the rent and buys the hours for the other thing, and a great many people did exactly that for years before anybody noticed what they were making. Being tired is not evidence of failure. It is the normal condition of financing your own project.

Be clear with yourself about which job is paying for which. Protect a small fixed amount of time for the thing you are building, even if it is three hours on a Sunday.