So maybe this time you messed up. Maybe this time you missed that opportunity.
What are you going to do next time? Make a plan, make it today.
Once, I heard someone say that living a holy life is just obeying God the next time he prompts. And then the next time, of course, and then the next. But rather than looking at the daunting 'for ever and ever', just focus on being prepared 'next time'.
The plan is the important part. The plan, covered in prayer. Because without a plan, you'll fall into the same things. At least I do. After all, it's easier to do something you've already done than to try something new.
"Fail to plan," they say, "and you plan to fail."
So use the motivation from this missed opportunity, this slip (or jump) into sin, this attitude-- use it for fuel for next time.
Only, don't wait for next time to make that plan.