Remind yourself about what happens when you don't tighten your strings. That is one way to tighten your strings. Reflect on the Dukkha of loose strings. When you are very keen, after a retreat is often the keenest time, you go home, you are practicing twice a day, you are really into it and then after some time it is kind of, oh, other things come up and you start to let your strings get loose. Some of you come back after one year and say, "It was great for the first 6 month and it was pretty good, but then the last two months... But I'm ready for the retreat…", ok, your strings got too loose.
One part of the Dukkha that comes from getting too loose in that way is that many people start to have a bit of self-hatred, they don't like the fact that they let the practice go. They don't feel good about themselves. Avoid that. It is very simple, avoid that, you don't want that Dukkha, out of compassion for yourself, don't loosen your strings that much. Very simple.
Now loosening strings in other ways, like your morality. What is going to happen if you fall backwards in your morality? You are going to hate yourself the minute you wake up to what you are doing, "Oh, I thought I had stopped drinking, I thought I had stopped…" You know, many people thought they had stopped but then they go and do it again, then again. Self-hatred comes up.
Every time you loosen your strings, look at what happens, look at how angry you get when you are not practicing enough Compassion/Lovingkindness. If you see the anger coming more and more, the frustration, the impatience, what is the reason for it? If you have had periods before when you actually could control your anger better and let go of your anger easier, what was the reason for that? Where you practicing harder? Probably yes.
Look at other things. What sort of TV and movies are you watching? How is that affecting you? Does that cause you to loosen your strings and is Dukkha involved in that? If so, avoid doing that and then automatically you are going to tightening your strings.
By reflecting on the Dukkha that comes from having strings that are too loose, this can often help us to tighten our strings. On top of that, every kind of problem that you have can be helped by having a good, kind, wise, spiritual friend, a Kalyanamitta. They may see that your strings are getting too loose, they may tell you, "Hey, you've got to change that." So having a good, kind, wise, spiritual friend is another way to tune your strings.