"Commitment" for me brings up the idea of "duty" and "obligation" based on "virtue" and "doing what is "right" ...but maybe that is just me
My current understanding of language and of how things are:
A commitment is always with myself. I declare to myself that I will (not) do something, and I make this declaration with full intent to follow through (for now; I may always change my mind on myself, but if I do that for minuscule reasons my intent was never truly full). The full intent to follow through is what changes a mere choice/decision into a commitment. A commitment which is fortified by using a 2nd commitment to not change my mind later (even in the light of new information) is called an unwavering commitment.
A promise is a commitment regarding benefits (and less commonly damages/duties) to someone other than myself. A feigned promise is the act of deceiving another with regards to that I do not, in fact, have any internal intent to follow through. (This is why a broken promise is a betrayal, unless the one who broke it did everything reasonably within their power to be true to their word.)
A contract is a promise, which creates legal duties and rights between two entities. A contract based on a feigned promise is made in bad faith. The romantic ideal of marriage was a special type of contract, because it entailed unwavering commitment and a powerful guarantor: the church/state.
I cannot have a contract between myself and "virtue", because it is not a 3rd party, but rather a mere concept within myself. To concepts, I can only be committed, but never obligated. This is called: being committed to a cause or to one's values.
If a contract is nullified, it is declared that one party did not or could not, in fact, develop the intent to follow through: there never was bilateral commitment. Examples might be getting married while intoxicated or contracts with kids (who cannot enter into contracts because they lack what it takes for informed consent).
If a contract is cancelled, (at least) one party changed their mind, committed to a different path, and now follows through with that new path; but the commitment was legally present at one point. That happens in one of two ways: I declare my change of mind to the other party and our relationship ends ordinarily (eg, I decide on a new mobile plan), or I fail to follow through and the relationship ends "for exceptional reasons" (eg, I failed to pay my bills).
Since I myself am merely a concept to myself, I should accept myself and commit to myself (even though I am not obligated to do so), because by doing so, I have to accept where/what I am now (acceptance), and also have to chose who I want to be (commitment). Without an acceptance of reality as it is, there would be no foundation for aimful/targeted action, and having a commitment always means having a should-be condition. Special case: By declaring the should-be condition to be equal to the current condition, I commit to keep things as they are; but even then, a should-be condition is (implicitly) being declared. The less clear I am about the should-be condition, the less strong my commitment can be. This is why it helps to have concrete goals, even if they change along the way.
People who do not commit are aimless and flakey. A sexual relationship without commitment is a fling.
The difference between choosing to have a good life and being committed to have a good life is in one's intent to actually make it so and follow through, instead of aimlessly wondering around, hoping for chance or fate to come to one's rescue, flaking out as soon as a hint of effort-required arises on the horizon.
In this way, it is not bad to have commitments to virtues: according to PD5 pleasure is kind of primus inter pares with prudence, propriety and justice. (We just need to keep our priorities straight and remember that no virtue is ever absolute or an end in itself.)