Showing up beats everything else. At the most basic, any program that you show up to regularly, complete regularly, and attend to will produce better results than the perfect routine that you barely ever do.
80% of the game is showing up, in some form which means it needs to be sustainable and for a program to be sustainable, it needs to be realistic, enjoyable, and above all flexible (REF).
In my past, I used to be an all-or-nothing fitness person. I'd either be giving it 130% or 0%. And if I wasn't giving it 130%, I would shame myself which led to 0% effort to avoid feeling shame.
It's important to do a self-assessment regularly to REF yourself.
Things I do to improve adherence
Long-term consistency beats short-term perfection.
1. Put it on the schedule
The times I have failed is when I don't have it on my schedule, on my calendar with specifics: 40 minutes at 6:30am on Sunday, Wednesday and Friday.
2. Be honest about what you enjoy
The times that I was my most fit, I was regularly doing activities I enjoyed. Aerial Arts, Parkour, Weight Lifting with friends.
The moment I stopped enjoying what I was doing, I started to fail.
3. Something is better than nothing
Life is unpredictable. My plan has to be flexible to adjust to life's demands. In my latest failure, I would use high stress, lack of sleep, low energy, etc to go to 0%.
And I would never plan for the eventual "shit, I have an appointment at 8am and I have to fast for it" days when I was supposed to work out and didn't. Now I have contingencies.
4. Non-exercise activity
Do things that aren't lifting. rock climbing, running, gardening. Anything that gets you moving on your rest days will help.
5. Never skip more than 1 day
Adherence is king. Even if it's a quick 10 minute bodyweight routine, something is better than nothing.
Injury
They happen. Adjust your workout accordingly to address the injury where you can. Use machines instead of free weights to avoid the injured area. See a doctor, of course. See a PT also.