The below is my understanding (which appears to have turned into somewhat of a ramble, perhaps):
Buddhism hinges on the concept of an "afterlife". If there is no "afterlife", then by committing suicide, there is the cessation of all feeling (vedanā). The Bahuvedanīya Sutta (MN 59)
describes various kinds of "pleasures", citing "cessation of perception & feeling" as a "pleasure" higher/more refined than all others, even though there is no feeling.
Similarly, the Nibbānasukha Sutta (AN 9.34)
speaks of Nibbana/Nirvana as pleasant, even though nothing is felt there.
Buddhism describes a continuum of experience or mindstream, but there is no absolute self to be found there. You are not the same person that you were ten years ago. It is also not just saying that the self you were back then is different than the self that you are now, since that is assuming a certain self in the first place. Assuming a self won't lead to liberation.
Assuming the Buddha's teaching is true, if one commits suicide with some craving left, the mindstream does not cease, and the mindstream continues into a different configuration (which can conceptually be referred to as a sense of being in a space, the "I am" conceit attached to a body in a "world", "realm", or "dimension", like "a hell", "a heaven", "human realm", "what it's like to be XYZ", etc.).
I trust there is such an "afterlife", not necessarily in terms described in the suttas or Christianity (e.g. swallowing red-hot iron balls--though I'm open to that being the case), but in more fundamentally mind-driven ways: hell could be a place of utter madness and chaos where the mind is tormented and despaired trying to make sense of a shattered and overwhelming experience, while heaven could be a place of greater subtletly, purity, silence, peace, benevolent intention, while a "lesser heaven" could simply be more ecstatic/hedonic.
Some will say that hell and heaven are "purely mental". I think they are purely mental in the same exact way that this present human existence is "purely mental" (whether it is or not). We are interested in phenomenology here, so whether things are purely mental or not doesn't really matter.
Buddhism is about how to lead your life in the present moment to be freed from suffering now and "for the rest of your life", but it is also about finding the absolute end of aging, sickness, and death (cf. MN 26
). This dreadful trio doesn't simply vanish upon death itself. When "birth is ended" upon full awakening, it is both in the present moment and "forever".
Buddhism thus teaches the afterlife and the cessation of the afterlife. Now this concept of an afterlife is difficult to be open to for most people brought up within the West (at least), within the consensus atheist-materialist-scientist paradigm; not only because it is difficult to prove, but more importantly because those within that paradigm tend to have a positive belief that there is no such thing as an afterlife, and the concept is often dismissed by principle as nonsensical. Small pieces of evidence are discarded as delusion or coincidence, with another "reasonable" yet undescribed reason being given. Shakespeare writes "There are more things in heaven and earth than are dreamt of in your philosophy". The universe is indeed strange and vast, with mind-boggling breadth of possibilities.
The good news
for you is that you don't need to believe in all this afterlife thing. You can practice Buddhist teachings and have them be immensely beneficial in the here-and-now. Having mundane right view (more or less: there is an afterlife, various "realms", and karma/kamma and its fruit) is beneficial as it encourages one to practice, but you can still practice without this mundane right view.
The Kālāma Sutta (AN 3.65)
mentions something that resembles Pascal's wager:
This noble disciple, Kālāmas, whose mind is in this way without enmity, without ill will, undefiled, and pure, has won four assurances in this very life.
- The first assurance he has won is this: ‘If there is another world, and if there is the fruit and result of good and bad deeds, it is possible that with the breakup of the body, after death, I will be reborn in a good destination, in a heavenly world.’
- The second assurance he has won is this: ‘If there is no other world, and there is no fruit and result of good and bad deeds, still right here, in this very life, I maintain myself in happiness, without enmity and ill will, free of trouble.
- The third assurance he has won is this: ‘Suppose evil comes to one who does evil. Then, when I have no evil intentions toward anyone, how can suffering afflict me, since I do no evil deed?’
- The fourth assurance he has won is this: ‘Suppose evil does not come to one who does evil. Then right here I see myself purified in both respects.’
but also this famous passage:
Come, Kālāmas, do not go by oral tradition, by lineage of teaching, by hearsay, by a collection of scriptures, by logical reasoning, by inferential reasoning, by reasoned cogitation, by the acceptance of a view after pondering it, by the seeming competence of a speaker, or because you think: ‘The ascetic is our guru.’ But when you know for yourselves: ‘These things are wholesome; these things are blameless; these things are praised by the wise; these things, if accepted and undertaken, lead to welfare and happiness,’ then you should live in accordance with them.
So, in the end, yes, Buddhist teachings include "heavens" and "hells", but that is not the most important point, and if you are not open to these aspects (or their descriptions), I hope it won't deter you from seeing the value in the rest of the teachings, the more important ones, which are visible here-and-now for yourself through direct experience.
I hope this is helpful and not misrepresentative of the Buddha's teachings.