assalamu alekum
I understand what you were feeling when you wrote this. As a matter of fact, I probably could've written it myself! Sometimes I think to myself, "if only I could keep consistent in salat, then I would have most everything all sewn up (spiritually speaking)".
...Then I started to realize that it was that very idea that revealed to me how it works with Allah and us and our ibadah, and how we really can do nothing on our own. If we could do all the things we know to do and should do, we probably wouldn't return to Allah again and again asking for His help, depending on His means to make a way for us to be obedient.
dear, there will be some days where you feel on top of your things come easily and consistently. But then there will be other days where it takes everything you have to do the bare minimum. I find myself thinking about all the days of my life...all the prayers I am "scheduled" to make before I die, and I get overwhelmed. I think of all the wudus and ghusls and fasts, and it all begins to seem utterly impossible.
I wish I could say that I have the perfect advice for you, the silver bullet to make salat more regular for you, but the truth is I (and many others I'm sure) are still trying to find that switch for ourselves. The best thing I've found to work so far is to treat each day like it is the only day I have to live, that each prayer is the only prayer I have to make for that day. If I miss a prayer, I try not to let it get me down (because thinking of all those missed prayers that must be made up can be very discouraging!). I try to move past it as if I did make it and worry only about the next ONE that needs to be made.
What encourages me is knowing each day is practice for making the next day better. What I didn't get right today, I will have a chance Insha'Allah to try again tomorrow. Some days we will fail, and some we will succeed, but it is our continual trying and not giving up that is going to make a lot of difference I believe, on judgment day.
Some days the best we can do is take heart in knowing how merciful Allah is, how He said if we were not a creation that sinned He would destroy us and make a new, imperfect creation that would ask for His forgiveness. I trust that He knows best of all our struggles, and as long as we continually turn to Him with our weaknesses, He will act justly with us.
I can say this with certainty, your heart is in the right place. As long as it remains sincere and yearning to submit to Allah, I believe Allah will Insha'Allah provide mercies for you when you need them regarding this issue.
may Allah Tala help us