You cannot. It does not exist. If you do happen to find any motivation it is temporary, fleeting, elusive. Motivation is a a false trigger designed by your primal self to get you to resolve an immediate issue, it is not designed to keep you going. If you are waiting, seeking, hoping for a constant feeling of motivation in your life to accomplish something or to be disciplined then you are going to fail. Repeat, motivation does not exist!
Now you many need a temporary mental change to help you change, or get started with something or to fix an issue that is causing you problems. If you want to call that motivation, go ahead. You can get that pretty easily. Listen to something inspiring, change your scenery, refocus your mind by writing things down, surround yourself with passionate people and many other tricks. However, if you want this feeling to be with you everyday, all the time, then too bad. Not going to happen.
So since motivation does not exist, and is not really a thing, what are you waiting for then? If you are waiting for motivation, you might as well be waiting for an angel from heaven to come down from the sky and bless you with super powers. Same difference. Both could happen, sure, but both are highly unlikely and both would require an absolutely clean and pure life style. Well, I do not have a clean and pure life style and I can bet you that you do not either.
So you might as well just get up and do what you need to get done. Just go. Now. Motivation is not going to come and visit tomorrow, or the next day, or on Sunday, or after the holidays. It certainly is not going to come next Monday morning and it rarely comes on your birthday. In fact it is never going to come, because it does not exist. So stop trying to find something that does not exist. Stop trying to find motivation.
Just do whatever you are dreading to do until it sucks so bad that you automatically do it anyway.